Questions for Andrew Rodney [Sitemap] - Digital Grin Photography Forum

rutt

Jul-03-2007, 07:48 AM

Andrew, I don't think you are being fair either to yourself or to Dan. Let me see if I can summarize both your ideas and his fairly. (Please feel free to correct or fine tune. I'm sure I understand Dan's philosophy better than yours, but I'm eager to learn both.)

Your philosophy:

Be a good photographer. Expose carefully. Give yourself the best possible starting point for post processing. Then use the best, most recent technology to help you use your eyes to perfect the image.

Dan's philosophy:

The human visual system captures in a very different way from the camera and adjusts in complex and different ways to viewing images in different media, for example, on the screen vs in print. What people remember seeing is often quite different than what the camera captures. What people see on even the best monitor with the best possible calibration may be quite different than what they see on a print, even one which "matches" the monitor perfectly. In particular, people adjust for casts best in real situations, second best on monitors, and least of all in print. Often it requires comparison with a color corrected version before people even notice the cast on their monitors.

Given all of this, the job of post processing is to make the image match the memory of the scene, express what we would have remembered seeing if we had been there. In pursuit of this goal, we'd like to have the largest possible tool box and best possible understanding of the actual theory behind the various techniques. The better this understanding, the better we'll be at applying the tools, and even improvising new ones as needed.

Just by the way I stated it, you can see that I have spent a lot more time thinking and writing about Dan's ideas than about yours. I'm eager for a better understanding of your ideas; I have your book and have been reading it; but I haven't yet found (or come to understand) your ideas at this level. So help me out.

But let's climb up and look down on this discussion from an even higher level. These are two radically different ways of thinking. I don't think anyone could deny that. And, I contend, they result in quite different looking images, at least they can in theory. Dan's approach would lead one to take more liberties with the image in order to bring make it seem more natural. Your approach will respect the original more.

I'd like to compare this to art traditions and theory. Impressionism was a very different theory of color and image sharpness than the classical school it supplanted. And the results were indeed very different. But I love both Goya and Monet. Cartier-Bresson and Ansel Adams had very different ideas of equipment, shooting, and the darkroom, but I love them both. In a way, what matters is not what they thought, but that they thought and devised coherent sets of ideas which in turn resulted in unique styles.

In short, it's more important to develop your own ideas and improve their internal integrity than to show that they are superior to others. We are not really operating in a area where it's clear that "better" has much meaning. Different people will find their own favorite way of working, of thinking about what they are doing, and finally their own style. And the variety of results and ideas is what makes it all so fascinating. Imagine a world where there was only Goya and no Monet!

I have the book! I stand by my points, especially when dealing initially with raw data. 90%+ of all such corrections can be accomplished faster, with better quality from the raw converter (assuming a good converter like ACR, LR or Raw Developer, the later which does provide LAB like controls over the raw rendering).

Much of the Lab like work can be done in RGB using Luminosity blend modes without spending the time to convert while throwing away a good deal of data (If you must, at least do it on 16-bit files).

arodney

Jul-03-2007, 08:45 AM

Dan's philosophy:
The human visual system captures in a very different way from the camera and adjusts in complex and different ways to viewing images in different media, for example, on the screen vs in print. What people remember seeing is often quite different than what the camera captures. What people see on even the best monitor with the best possible calibration may be quite different than what they see on a print, even one which "matches" the monitor perfectly. In particular, people adjust for casts best in real situations, second best on monitors, and least of all in print. Often it requires comparison with a color corrected version before people even notice the cast on their monitors.

I've never heard Dan say this and in fact, it's more of my philosophy in that the digital camera and our visual system ARE very different. This goes back to the idea of scene referred versus output referred colorimetery of which I co-authored this paper for the ICC:

http://www.color.org/ICC_white_paper_20_Digital_photography_color_manag ement_basics.pdf

There's only one accurate color; the measured color of the scene. That's scene referred and doesn't look at all nice on an output referred device (a display or a print). The job of the raw converter and user is to make output referred images that express what they want to represent on some output device. This isn't image correction. Its image creation just as the color negative wasn't a reference to the photographed scene, someone had to print it, using some set of color filters to produce the desired color appearance and deal with the orange mask.

Given all of this, the job of post processing is to make the image match the memory of the scene, express what we would have remembered seeing if we had been there. In pursuit of this goal, we'd like to have the largest possible tool box and best possible understanding of the actual theory behind the various techniques.

Did Dan say that? Because I have lots of posts of his where he dismisses the use of wide gamut working space like ProPhoto RGB which is absolutely necessary if you want that larger toolbox. Same with working with high bit data yet Dan for years has dismissed the use of 16-bit files in Photoshop and challenged (unfairly, see URL below) that this has any advantage for our bigger toolbox when the math is undeniable.

This is useful to review in context to the so called 16-bit challenge:

http://www.brucelindbloom.com/DanMargulis.html

Dan's approach would lead one to take more liberties with the image in order to bring make it seem more natural. Your approach will respect the original more.

Not at all, just the opposite. In fact, if you subscribe to his list, you'll recall an exercise submitted by a photographer who had issues with the image captured JPEG of a night scene and buildings. Dan discussed setting the cement to be BTN (his term for By The Numbers) neutral. But it made the image look ridiculously poor IMHO as well as others because the scene was supposed to have a color cast, it was shot at night! My take would be, use whatever rendering controls available in your raw converter to produce color and tone you prefer and wish to express about the image. Lets not forget raw is Grayscale data, you have to build the color (tone). Even if you have a converter that would provide scene referred rendering, it would look pretty awful on screen (that's output referred). You have to apply toning here at the very least, probably some saturation boast and WB.

Dan's also of the impression that JPEG is the way to go and not messing with Raw OR lock down the raw converter to give you flat data and correct in Photoshop. This is time consuming, not at all good for the quality of the data and dismisses a lot of the power in metadata editing of raw, linear data. But he really doesn't (yet) understand raw workflows (one file I submitted to the list as a DNG was rejected by Dan because its not the raw file according to him; I have the posts where he says this). But let me leave you with his quote about ACR and JPEG since we really disagree here on both the toolset and file formats one should be editing initially:

On 2/5/07 5:52 PM, "DMargulis@aol.com" wrote:
Lee Varis writes,

<< Given the limitations of the interface (and please, this is obvious
regardless of features like Vibrance) Dan has suggested taking a
conservative approach to the adjustments you apply in ACR. ( Andrew,
before you jump on this, please READ Dan's book) This makes perfect
sense in a "one image at a time" workflow. However, for many
photographers this is not practical when dealing with a large volume
of images that have to be delivered to a client. Fortunately, if
you've done your homework and tested your camera to optimize your ACR
settings (at least visually) to your shooting style, you shouldn't
have to do that much in ACR to get a reasonably good image. >>

Quite right. I write only to point out that the book clearly states that it is, as you say, only discussing "one image at a time" workflows. Camera Raw has nice features for processing batches of images but they are beyond the scope of what I write about.

Similarly, we all have occasions when we are unwilling to spend time on
images even when we know we might get better quality if we took a few minutes more. In such cases, of course I have no issue with someone who tries to get a fast result in Camera Raw and call it quits there.

It does, however, beg the question: if saving time is so important that
quality compromises need to be made, why is the raw format being used at all? With rare image-specific exceptions, essentially anybody who is not a beginner will get better final results by shooting JPEG and correcting in Photoshop than an expert can who shoots raw but is not allowed to do any manipulation outside of the acquisition module,And in less time, too.**The idea of a raw module is to *empower* the image-manipulation program, not replace it.

Dan Margulis

**This is silly, I've challenged him to do this at PhotoPlus or Photoshop world, he's ignored it.

We fundamentally disagree on the toolbox itself.

rutt

Jul-03-2007, 10:22 AM

I liked the beginning of your post more than the end. You put yourself in the best light when you express your ideas positively instead of explaining why Dan is wrong. Convince me that you are right instead. That's how Dan hooked me in the first place. I had problems, went in search of solutions, and found that Dan's books contained ideas that worked to solve them.
Over the years, I found many solutions to my problems in his writings.

My least favorite part of PP5E are those middle chapters which dwell on how Dan was right and the other guys were wrong about 8 vs 16 bits, color management, color spaces, &etc. It just doesn't matter to me who is right and who is wrong. As I said, I'm pretty sure there isn't any such thing in this domain.

So please let's avoid that trap, take the high road, and explain what you think and show how well it works. That will keep my attention.

A good place to start would be my statement of your philosophy. I was really hoping you'd flesh it out come up with something that more accurately represents what you think. I'm very familiar with Dan's work, but less with yours. Help me understand.

Duffy Pratt

Jul-03-2007, 10:44 AM

The first URL in Andrew's post is broken.

Duffy

patch29

Jul-03-2007, 11:35 AM

The first URL in Andrew's post is broken.

Duffy

I think the link can be found on this page (http://www.color.org/whitepapers.xalter).

Look for

Digital photography color management basics

nikos

Jul-03-2007, 11:41 AM

Much of the Lab like work can be done in RGB using Luminosity blend modes without spending the time to convert while throwing away a good deal of data (If you must, at least do it on 16-bit files).

If I remember correctly, Dan Margulis tested out a file and converted it from RGB to Lab to RGB etc. numerous times with no or inconsequential signs of degradation. This was in his Lab book.

You're stating quite the contrary by saying that "a good deal of data" is being tossed. Have you experienced this first hand or are you making an assumption.

Thanks,
Nikos

(http://www.google.com/search?num=50&hl=en&safe=off&client=firefox-a&rls=org.mozilla:en-US:official&hs=Vk7&sa=X&oi=spell&resnum=0&ct=result&cd=1&q=inconsequential+&spell=1) (http://www.google.com/search?num=50&hl=en&safe=off&client=firefox-a&rls=org.mozilla:en-US:official&hs=Vk7&sa=X&oi=spell&resnum=0&ct=result&cd=1&q=inconsequential+&spell=1)

arodney

Jul-03-2007, 12:10 PM

If I remember correctly, Dan Margulis tested out a file and converted it from RGB to Lab to RGB etc. numerous times with no or inconsequential signs of degradation. This was in his Lab book.

Well the test is far from conclusive and the damage isn't always inconsequential. First off, any data loss in an image adds up to the point where, depending on the image and output device, the result is banding. When will this happen? We don't know. We do know that these kinds of edits (all edits in fact) amount to data loss. So doing a few rounds of back and forth and printing a single image ink on paper to a course linescreen doesn't tell us a lot. What about a much finer, contone device? What about after applying more edits? IF you do this in high bit, something Dan dismisses, its not an issue. You have far more data than you need (up until more device drivers accept and use more than 8-bits per channel. Some today do, for example, any Epson that's driven by the ImagePrint RIP).

You're stating quite the contrary by saying that "a good deal of data" is being tossed. Have you experienced this first hand or are you making an assumption.

Good deal? That's not something I can define for you specifically but I can give you exact numbers and you can decide if that's a good deal or not (and just for this one set of edits). For me, its a good deal percentage wise, especially in ProPhoto RGB, the space I use (and always in high bit).

Depending on the working space, for example, going from Adobe RGB, which has 256 values available, converting to 8- bit LAB reduces the data down to 234 values.The net result is a loss of 22 levels. Doing the same conversions from ProPhoto RGB reduces the data to only 225 values,producing a loss of 31 levels.

When and will you see this? Hard to say. The math is undeniable. So you start out with a file in 8-bit with smooth gradients like a sky, or the bumper on a car. At what point will banding result on your output device? It might not, but it does happen, its something you don't have to worry about if you simply work in high bit:

http://www.digitalphotopro.com/articles/2007/janfeb/bitdepth.php

arodney

Jul-03-2007, 12:13 PM

I think the link can be found on this page (http://www.color.org/whitepapers.xalter).

Look for

Digital photography color management basics

Direct link:

http://www.color.org/documents/ICC_white_paper_20_Digital_photography_color_manag ement_basics.pdf

Duffy Pratt

Jul-03-2007, 12:25 PM

arodney

Jul-03-2007, 12:37 PM

Thanks for posting a working link.

I'm a bit confused by the jargon, or even the need for jargon here. I think I have something of a handle on "output referred." That seems to mean what the image ultimately looks like when displayed by some output device.

Exactly.

But I don't understand "scene referred" at all. Does it mean what the photographer saw when shooting?

Its what the capture device recorded. So if you went into the field, measured the illuminant, some colors in the scene, calculated the dynamic range and could record as much of that as possible with the current technology, what the device 'saw' and captured would be scene referred.

Some raw converters allow you to get to this data. The linear encoded data when not output referred looks pretty ugly (there's an example in the PDF). Flat, dark, it needs a saturation boast, a tone curve etc. This is what the in camera processing does (based on a matrix or look setting) when it creates the JPEG. You have no control, other than the look settings, over the scene to output referred conversions.

The only way to display something that was scene referred, I think, is on some monitor or in some print. And once you do that, the image has been rendered and is no longer scene referred.

You could send the scene referred numbers to a display or print but it would look pretty ugly. But this is accurate color! When photographers say they want accurate color, they don't really know what they are asking for. Accurate can only really be defined by the measured color of the scene. This is scene referred. What we really want is pleasing color, color that appears as we wish to express what we think (or remember if you buy that) of the scene. That's output referred.

So when people talk about accurate color, or working by the numbers, you have to ask them just what they really want. If you're doing copy work of fine art in the studio, you control the dynamic range, the color of the lighting etc. You DO want Scene Referred color. It might be exactly right for reproduction of the art work with perhaps minimal tweaking for output referred. But for just about anything else, the results are not pleasing color, not color anyone would say appeared as they or you saw it at the scene. Look at the huge dynamic range differences between scene and print. At noon, full sun, you might have a 10,000:1 contrast ratio. On a print, even a fine art ink jet, you might be lucky to get 450:1 ratio. Got to squeeze on into the other. That's what rendering is all about in a raw converter. That and more.

Duffy Pratt

Jul-03-2007, 12:54 PM

You could send the scene referred numbers to a display or print but it would look pretty ugly. But this is accurate color! When photographers say they want accurate color, they don't really know what they are asking for. Accurate can only really be defined by the measured color of the scene. This is scene referred. What we really want is pleasing color, color that appears as we wish to express what we think (or remember if you buy that) of the scene. That's output referred.

If a process yields colors which so obviously look wrong, I think its not a good idea to insist on calling those colors "accurate." There may not be any purely scientific way to prove that some other outcome is "accurate" or not. In that case, what you we are left with is a) the client rules or b) the majority rules. I'm not a scientist and I can live with that flexibility. It makes alot more sense to me than taking some machine produced vision that is obviously wrong and declaring it "accurate" for some reason.

Basically, if what machines see, without further massaging, is both ugly and looks very different from what the scene looked like to the photographer, then I see even less reason to call the machine's rendition "accurate" than I would the photographer's unreliable memory. But whatever you call it, as a practical matter, I'm not very interested in it. The intellectual side of me thinks its a pretty cool curiousity, but I fail to see how any of this knowledge is going to help me make better pictures. (And that may well be my failing.)

Duffy

rutt

Jul-03-2007, 01:07 PM

Here is a different way to think about this. Von Gough's "output device" compares pretty poorly to a good modern monitor in terms of gamut and dynamic range. Yet we don't feel that when we look at The Bridge at Arles. Walk into the Venice room of the Turner exhibit at the Tate and you can almost feel the warmth of the sun. Yet, he also worked with a very limited dynamic range and gamut.

Go to a museum, buy a print of one of these paintings, take it back into the gallery, and hold up next to the original. Not so good.

Something very subtle is going on. Somehow, these guys manage to trick your visual system into seeing something very different than what is there on the canvas. And it's very fragile. Change the colors just a little bit and the effect is ruined. Reproduce at a different size and the effect is diminished.

Another more practical question, Andrew. Here is an experience I've had dozens of times here on dgrin. Someone posts a shot for critique. Looks pretty good on my calibrated monitor. But just to check I download and discover that the squirrel is blue, the horse is purple, the face is magenta, the dog is pink, &etc. You know what I mean. I use curves of some sort to push the colors toward away from the impossible and toward the possible. And presto-chango, it looks 100% better, the photographer thinks so, all the other viewers think so. But nobody saw it from looking at the original. If you like I'll dig up some of these dgrin threads. There are a lot of them.

I know I've told this storry in Margulis-inspired language. Let's not waste words saying what was wrong about this. Instead tell me what happens in your workflow. What detects the possibility of this kind of improvement?

arodney

Jul-03-2007, 01:10 PM

If a process yields colors which so obviously look wrong, I think its not a good idea to insist on calling those colors "accurate."

They are not wrong, they are simply not optimized for the current viewing media. Is a color neg wrong? It doesn't look like the scene.

If you shoot both Velvia and Ektakcrome of the exact same scene, do they look identical? No. Which is accurate? Actually neither.

I'd prefer to call it preferred or pleasing. Its real difficult to put a delta on accurate unless you use some way to measure the color and provide some numeric way of defining how close those colors are. Of course, if you want to use accurate, fine but I think it dilutes its meaning, it makes talking about such conditions ambiguous and in the end, is always up to interpretation.

When you measure something, using some kind of reference grade measuring device, its pretty easy to express whether what you're measuring is accurate or not. Now if I was building a deck, I'd use a measuring tape instead of my foot, even though my foot is pretty close to 12 inchs. I don't need a ruler that's accurate to 1/10000 of an inch although measuring such distances can be done. But saying that using your foot to do this provides an accurate way to build the deck is a bit of a stretch.

There may not be any purely scientific way to prove that some other outcome is "accurate" or not.

Yet there are ways of doing this.

In that case, what you we are left with is a) the client rules or b) the majority rules. I'm not a scientist and I can live with that flexibility. It makes alot more sense to me than taking some machine produced vision that is obviously wrong and declaring it "accurate" for some reason.

Again, this is boiling down to semantics. But others do want accurate color, or they need a way to define what that means and we have the instruments and processes to do this. So I don't see why we should dilute the term. Pleasing color, color the client loves, color you love, that's all fine.

Basically, if what machines see, without further massaging, is both ugly and looks very different from what the scene looked like to the photographer, then I see even less reason to call the machine's rendition "accurate" than I would the photographer's unreliable memory.

One we can measure, one we can't. On is based on empirical data, the other isn't. That doesn't make one right for you, but, if you want to really know, based on some unit of measure if two colors match (without getting into human perception and the effect of optical illusions), then its useful to define accurate based on some measurements of an instrument.

Try looking at this optical illusion. The two patches are the same, they measure the same, they don't look the same. Are they accurate based on what they really are or how you see them?

http://web.mit.edu/persci/people/adelson/checkershadow_illusion.html

But whatever you call it, as a practical matter, I'm not very interested in it. The intellectual side of me thinks its a pretty cool curiousity, but I fail to see how any of this knowledge is going to help me make better pictures. (And that may well be my failing.)

If you understand the process and the limitations of the capture device, if you understand what a raw processor is actually doing and you don't use incorrect terms to ask for something (like accurate color), you have a better chance of getting what you wish. Yes, its a very practical matter.

Duffy Pratt

Jul-03-2007, 04:10 PM

Wouldn't it be fairer to say that using 16 bit editing, it will take more edits and more severe edits before banding would become an issue. The mathematical principles are the same whether you are dealing with 8 bit or 16 bit. At some, as yet unknown point, the manipulation of the data will lead to visible banding.

Right now, there are some who bemoan banding in the manipulation of 8 bit images (though I have never encountered any in the work I've been doing). I can readily imagine that when 32 bit becomes the norm, a bunch of people will say that you should do all your editing there, "just to be safe," because you never know when the banding will become visible, or when it will become an issue with the newest, latest, coolest output devices.

The people who advocate using higher bit processing are definitely correct on their theory. The interesting thing is that that theory has so little real world practical application. Someday it might. I've tried the repeated conversion from RGB to LAB and back, making edits in between. I've done it on several pictures and have not been able to see any meaningful differences between the two. (By that, I mean that I haven't been able to find any areas where I could definitely say that one was superior to the other.) As a result, I typically don't hesitate to make a conversion to LAB and back.

I also sometimes use Fade/Luminance to save time. I feel confidant in doing this as an alternative, because I know the types of images where this move will not be same as moving to LAB, and thus know when moving to LAB will make an actual difference. (This happens where extremely light areas of color will get halos that are completely blown. That will give a light colored object with a pure white halo when using Fade, but will give colored halos when taking the trip to LAB and back).

As long as I'm saving the original files, I'm not to concerned with intermediate data for its own sake. If losing data makes the final output better, then I'm all for chucking the data. If losing data will save time and give the same output, then fine. The only time I would really be concerned with throwing away data through edits is when it makes the final product I'm aiming for look worse.

And I'm not concerned with other possible final products that I might make in the future. I'm still learning this stuff and the technology is improving all the time. If, in a couple of years, I want to make a big print of something I took this year, I will start from scratch on the original and use the best I know how to get the result. I suspect that I will be able to do better in two years than I could do now. And since I'm improving my skills, and the number of old pictures that I'm interested tends to dwindle over time, I am not all to concerned with saving the "how" of my current work.

Duffy

arodney

Jul-03-2007, 05:25 PM

Wouldn't it be fairer to say that using 16 bit editing, it will take more edits and more severe edits before banding would become an issue. The mathematical principles are the same whether you are dealing with 8 bit or 16 bit. At some, as yet unknown point, the manipulation of the data will lead to visible banding.

Absolutely true. But lets look at the huge difference. An 8-bt file has 256 levels per color. A 12 bit file has 4096. Most camera provide at least 12 bits of data. Its providing this data from the get go for you. Why throw it away? Sending the best 256 values from 4096 is all we need at the very least.

I can readily imagine that when 32 bit becomes the norm, a bunch of people will say that you should do all your editing there, "just to be safe," because you never know when the banding will become visible, or when it will become an issue with the newest, latest, coolest output devices.

We'll need that for true HDR capture which will be amazing. PS supports its. The Adobe engineers don't put this stuff in for no reason. Look at all the increased high bit capabilities staring in Photoshop 5.

The people who advocate using higher bit processing are definitely correct on their theory. The interesting thing is that that theory has so little real world practical application.

Says who? How many high bit captures and images edited in that fashion since PS5?

I've tried the repeated conversion from RGB to LAB and back, making edits in between. I've done it on several pictures and have not been able to see any meaningful differences between the two.

I don't know what meaningful means to you (I know what it means to me). So the statement doesn't wash, it kind of sounds like Dan.

We also don't know what future output device or edits will be used.

I'm not suggesting you don't edit the numbers because there is resulting data loss. The very reason we use applications like Photoshop is to alter the numbers to provide better color appearance at the price of data loss. Of course, if you do all this at the raw rendering stage, there truly is no data loss! But none the less, once in Photoshop in high bit, no worries. You want to lose 31 of your 4096 levels by going into and out of LAB, so be it. If you want to do this on 8-bit, I'd have to wonder when, and why you tossed all the other data.

I also sometimes use Fade/Luminance to save time.

And bits. But really, with high bit data, the data you're capture device is providing anyway, no worries. But it is useful to know the benefits of Luminosity blend modes.

I'm still learning this stuff and the technology is improving all the time.

Which is why I question Dan's negativity towads both high bit data and wide gamut spaces, both or which ensure the data you started with can be used as technology improves. Go back say 3-4 years ago, the prevailing logic was that Adobe RGB (1998) would be fine as an encoding color space due to the output technology and gamut. Today, we have both Canon and Epson inks that exceed Adobe RGB gamut.

pathfinder

Jul-03-2007, 07:23 PM

I am late to the party, and under dressed. ( rutt please notice that lack of a smiley here out of respect for you )

I was initially not very pleased with my digital images, until I gave up the idea that they were "captured by the camera". I gradually came to accept that images we see published are not "as captured by the camera" despite many statements by photographers that they have not been manipulated, that they were just as captured. This is like folks who drop off a Kodachrome to be printed in a book, and say "do not manipulate it". It is impossible to match the color and the brightness ratios of a Kodachrome slide on a printed (online CMYK ) page. Someone has to do the pre-press prepping to get the slide's lighting ratios to fit onto the page. Just as the engineer's at Kodak, created the curves to allow Kodachrome to capture an illusion of the lighting ratios of reality on film itself.

I KNOW that the colors and the lighting ratios in my images captured by my digital camera NEED to be altered when post processed by me as I edit them for printing or posting on the web. My images are creations of my mind, written into the digitally captured image data caught by my camera. I do not want to make this sound like I am suggesting that my images are Photoshop artistic drawings - they are photographs, not drawings or renderings - that have been altered to more closely match what I saw in my mind's eye when I pressed the shutter.

I do not know about "accurate " color - I do know how I think my images should look in order to be more pleasing to the eye of the viewer.

I do confess to using the RGB numbers to evaluate how neutrals should be represented. But I also feel free to ignore this data if I so choose. Usually I find it helpful to understand what the pixel data is saying about colors.

I love Adelson's Illusion (http://web.mit.edu/persci/people/adelson/checkershadow_illusion.html) - Is that the right word?? Are the colors "accurate" here? What does the word 'accurate' really mean in this context. Colorimeter accurate or "looks" accuarate?

Interesting discussion - I look forward to learning more as it progresses.

rutt

Jul-04-2007, 06:05 AM

Andrew, I don't think you addressed this question, perhaps because I buried it beneath a defuse and not very practical observation.

But for me, this is a key question. It's maybe the most important thing I have learned from Dan. Do you do the same thing? Something else?

Another more practical question, Andrew. Here is an experience I've had dozens of times here on dgrin. Someone posts a shot for critique. Looks pretty good on my calibrated monitor. But just to check I download and discover that the squirrel is blue, the horse is purple, the face is magenta, the dog is pink, &etc. You know what I mean. I use curves of some sort to push the colors toward away from the impossible and toward the possible. And presto-chango, it looks 100% better, the photographer thinks so, all the other viewers think so. But nobody saw it from looking at the original. If you like I'll dig up some of these dgrin threads. There are a lot of them.

I know I've told this storry in Margulis-inspired language. Let's not waste words saying what was wrong about this. Instead tell me what happens in your workflow. What detects the possibility of this kind of improvement?

arodney

Jul-04-2007, 07:59 AM

I do confess to using the RGB numbers to evaluate how neutrals should be represented. But I also feel free to ignore this data if I so choose. Usually I find it helpful to understand what the pixel data is saying about colors.

Neutrality defined numerically along with values for highlight and shadow (and saturation clipping on either end) are about the most important, some would say only useful numbers you need to memorize.

Note that not all RGB color spaces behave this way! RGB color spaces from capture devices (scanners) and printers do not always define a neutral where R=G=B. All RGB working spaces, which are mathematically constructed do. We call these 'well behaved' color spaces. For fun, make a neutral in your working space, convert to an RGB print space (for your Epson, Canon etc) and now view the RGB numbers. They are not equal.

I love Adelson's Illusion (http://web.mit.edu/persci/people/adelson/checkershadow_illusion.html) - Is that the right word?? Are the colors "accurate" here? What does the word 'accurate' really mean in this context. Colorimeter accurate or "looks" accuarate?

I have lots of URL's with similar optical illusions. Its helpful in showing users the necessity of using instruments instead of our eyes for SOME tasks. Our visual system is poor at viewing solids like this (where a colorimeter would of course measure accuractly by defining both squares as the same color). That would be accurate color. That our visual system is fooled and we think we see two different colors (even if we prefer this rendering), its clearly not accurate. Instruments are found in our kitchens, cars and airplanes among others for good reason.

Our visual system is much better than instruments at viewing colors in context. An image is a prefect example. One could look at a night shot and gray balance the cement in the foreground only to see that this ruins the color appearance desired by the image creator. This BTN (By The Numbers) approach doesn't work. Same with a sunset scene.

So, pleasing color may not be, and often isn't accurate (measured) color but most of the time, we want pleasing color. Using the term accurate color without defining what is meant by accurate and not backing that up with some measurement isn't a useful way to describe color. Least we forget, all these computers understand are numbers. What is Red? Its a word we use to define a sensations in our brain. What color is R234/0/0? Well its some shade of red but is that tomato red? Numbers alone don't define color appearance unless you're using LAB which is based on human vision.

arodney

Jul-04-2007, 08:10 AM

Another more practical question, Andrew. Here is an experience I've had dozens of times here on dgrin. Someone posts a shot for critique. Looks pretty good on my calibrated monitor. But just to check I download and discover that the squirrel is blue, the horse is purple, the face is magenta, the dog is pink, &etc. You know what I mean.
Not really. First you say you view the image on a calibrated display and it looks good. Then you download it and it looks bad and you feel you need to fix it. This is clearly a color management issue from the start. Why are the same set of numbers providing two grossly different color apparences?

You have to figure out what's broke before you just dig in Dan style and alter the numbers.

I can provide you an image that appears at least 2 stops under exposed and I can fix this without altering a single color number. You can view an image that is numerically perfect (on your calibrated display) then open it in a web browser and it looks totally different and wrong. Do you alter the numbers when in fact, there's nothing wrong with them?

If you opened an image on your system and it looked too dark, you wouldn’t crank up the luminance on your display to fix this problem right? Initially you'd want to alter the numbers. But the fact is, there are plenty of situations where the numbers are fine, the application simply isn't providing you the correct preview. This is often seen when users don't post sRGB to the web but it extends to other areas, even Photoshop.

So I can't answer your question because something other than the numbers in the document seem to be wrong. Why do they look OK when properly viewed on a calibrated and profiled display within a color managed application but not elsewhere (the elsewhere you haven't defined). This could be a color management issue, an application issue or a number issue but I'd only be guessing without getting further info from you and how you've handled the document in both cases.

With proper color management, the numbers and associated color space (you have to have a color space or the numbers are meaningless) should provide the same color previews to all users who handle them properly, meaning in a color managed application using a profiled display. Outside that, all bets are off.

Avoid the temptation to change the numbers until you know that's what is required to fix the color appearance.

rutt

Jul-04-2007, 08:10 AM

Nice post, Andrew. It helps me understand your position.

But I still have the question. Do you have some way to test for impossible colors which we might not notice until they are "corrected" after which everyone prefers the new version? Maybe you don't accept the premise that the image looks better after the squirrels no longer measure negative in one or both of A and B, &etc. I've had a lot of experiences which lead me to believe that people nearly always prefer these corrections over the originals except in rare cases. (Those rare case are when we are trying to show interesting lighting or even more interesting interactions of lighting. This is an interesting topic all by itself, but please let's focus on the common case first.)

arodney

Jul-04-2007, 08:15 AM

But I still have the question. Do you have some way to test for impossible colors which we might not notice until they are "corrected" after which everyone prefers the new version?

Impossible colors. That's a Dan term, you better tell me what you feel it means.

There are out of gamut colors.

There are colors in some color spaces that are defined that are not visible to the human observer (this is rare and not really a big problem unless you go out of your way to define them numerically which isn't useful).

rutt

Jul-04-2007, 08:19 AM

Not really. First you say you view the image on a calibrated display and it looks good. Then you download it and it looks bad and you feel you need to fix it. This is clearly a color management issue from the start. Why are the same set of numbers providing two grossly different color apparences?

No, that's not what happens at all. Here is what happens:

Someone posts an image on dgrin for critique.
It gets basically positive responses.
It looks OK to me on my calibrated monitor
Just for fun I download and open in Photoshop
Looks the same as in the browser
I measure the face, sky, squirrel, horse, whatever and find a reading that I don't think should be possible. For example, the squirrel measures negative in either A and/or B.
I "correct" somehow to push the reading toward what I think is possible.
Now comparing before/after, it's obviously a big improvement. In fact, I wonder why I didn't notice it at first.
I post the "corrected" version. Everyone prefers it.

So I don't think this is a color management issue, at least not one I understand.

arodney

Jul-04-2007, 08:27 AM

No, that's not what happens at all. Here is what happens:

Someone posts an image on dgrin for critique.
It gets basically positive responses.
It looks OK to me on my calibrated monitor
Just for fun I download and open in Photoshop
Looks the same as in the browser
I measure the face, sky, squirrel, horse, whatever and find a reading that I don't think should be possible. For example, the squirrel measures negative in either A and/or B.
I "correct" somehow to push the reading toward what I think is possible.
Now comparing before/after, it's obviously a big improvement. In fact, I wonder why I didn't notice it at first.
I post the "corrected" version. Everyone prefers it.

So I don't think this is a color management issue, at least not one I understand.

First of all, the image is probably not previewing identically on the browser and Photoshop unless you're viewing that image in Safari but I digress.

As to why it didn't occur at first, you'd have to ask the originator of the image. Did they post it because they didn't like the color appearance? Did they work with a calibrated display as well? Are you just a lot better at altering the color apparence? Why wasn't the color fixed on acquisition (at the scan stage or raw conversion)? IF a film scan, did it match the film and was the purpose to match or improve the original?

What your telling me is you see images that you don't think appear as good as they should be, you alter the numbers and everyone (everyone?) agrees its better. You are validating your ability to use an image editor to improve the image which I heartily buy. It doesn't tell us much about the original person handling the image and what issues they had or didn't have.

I guess I'm not sure what your point is, other than you looked at the image (or looked at the numbers) and altered them and improved the image.

rutt

Jul-04-2007, 08:38 AM

arodney

Jul-04-2007, 08:46 AM

Yes, I agree, Dan uses this term in two different ways.

To describe LAB colors such as L=0, A=0, B=-128. We could discuss the semantics of the word, "impossible" as applied to these, but it's not what I mean in this instance, so it would be a digression.
To describe evidence of a cast. For example human faces which measure negative in either A and/or B, midday skies which measure strongly negative in A, wedding dresses no neutral. This is what I was trying to describe. As I said, I apologize for using Dan's language, but he taught me to do this and it has proved to be a useful thing to do.

There's no such thing as an impossible color when defined in LAB, it defines (with some holes) human vision based on its daddy, CIEXYZ.

We've talked about describing a cast using the original RGB working space and the fact that, lots of images need a color cast.

Its quick and easy to simply LOOK at the image in context, something I've discussed, then fiddle around looking at LAB numbers that tell you that the image you like is wrong. I'd frankly be looking at the source color space numbers (in my case, ProPhoto RGB).

I would submit that all wedding dress images should not be neutral while some should be, but it seems easy just to look at the image and make the decision.

If you're asking me if the first thing I recommend you do is mouse around an image and look for odd color values, my answer would be no. I' look at the entire image first and see if I think it needs work or not. Much of this work BTW would take place in my raw converter (or going back in time, on my film scanner).

rutt

Jul-04-2007, 08:49 AM

First of all, the image is probably not previewing identically on the browser and Photoshop unless you're viewing that image in Safari but I digress.

Yes it's a digression, but for a majority of images, it's so close that I can't tell the difference. Maybe my eyes aren't good enough. Sometimes, though you are right, and it really doesn't look the same. You've taught me to understand why in private correspondence. But we digress.

I guess I'm not sure what your point is, other than you looked at the image (or looked at the numbers) and altered them and improved the image.

My point is that I wouldn't have known to try the particular improvement (better word than correction, thanks) unless I had measured and had some ideas about what the numbers should be. Not just the originator, but everyone(!), prefers the improved version, but until I measured, nobody(!) was particularly dissatisfied with the image.

I have a theory about why this happens. But this thread isn't about my ideas, it's about yours. I'd like to know if there is a way of understand this story which you buy into. I'd like to know if you have an alternative way of detecting that an image is a candidate for this kind of improvement.

arodney

Jul-04-2007, 09:02 AM

My point is that I wouldn't have known to try the particular improvement (better word than correction, thanks) unless I had measured and had some ideas about what the numbers should be.

Numbers are important but not to be used without looking at the color appearance they produce. Numbers based on what too? There are no capture or output devices that handle Lab. There's only one 'device' it defines, that's the human observer (you and I).

In an RGB working space, an editing space that is well behaved for editing and archiving, you have some useful numbers to look at as I described but you don't need to go overboard and only rely on them. The best approach in my book is to use the numbers, where useful and the calibrated display.

Then, if you want to output the numbers to any device other than that display, you need an output profile which will produce the correct numeric conversions from the original and handle the gamut mapping issues. The numbers provided for the output device are correct (assuming a good output profile). At some point you have to soft proof this, look at the image with the dynamic range being used (Paper white, ink black) and decide if what you're seeing is what you want to reproduce on the output device. The LAB numbers, any numbers other than for the output device are immaterial.

patch29

Jul-04-2007, 09:11 AM

Rutt can you link to some of the examples you describe?

and/or can Andy pick an image and each of you can post your version?

edgework

Jul-04-2007, 09:12 AM

I just read all the posts in this thread and quite probably have missed some points here and there. Nonetheless, here are a few observations, off the top of my head:

Andrew—your knowledge and credentials are obvious and need no qualification, but forgive me if I say that you sound like you're all strategy and no tactics. Anyone who can acknowledge that "accurate color" will, nonetheless, be ugly color that pleases no one, yet not realize that the argument is essentially meaningless beyond that point, is mistaking theory for results.

I've been producing color for magazine covers, photospreads, photographers and web sites, for nearly 20 years, and doing it well. I've plied my craft in shops that spit on the notion of color management, and I've done it in shops that worship the concept like it was the salvation of western civilization. I'm curently working in an environment that typifies most such environments: they pay lip service to the idea but really don't do it well.

When we acquired a new proofing system a while back, our production wizard ordered up a proof from our old provider to compare with ours. Shock of shocks, they didn't match. So he emarked on a city wide quest, ordering contract proofs from about a dozen different services. All were different. There's nothing more pathetic than a so-called production wizard staring at a pile of proofs that don't match and wailing "Which one is correct?" I told him "The one with the client's initials in the lower right corner, the one a printer contracts to match on press. That's your correct color." That's tactics.

Rutt makes a passionate case for Dan Margulis' approach, by the numbers, you make a passionate case for dismissing Rutt's case, also based on numbers... numbers, schmumbers. What we have here are photographers looking for tactics and theory be damned. Personally, I don't believe you fail to understand the point Rutt made in his last post; you're too smart. Talk all you want about this space or that profile, in the real world, when you need results, taking a look at the numbers and noting some general patterns about relationships between the different channels, is not only warranted, to refuse to do so is amateurish and to deny the usefulness ceases to be an artistic, or scientific, argument, and becomes mere politics.

The myth of color management rests on the notion that there exists, somewhere, a device independent definition of color from which all others can be measured, and which can serve as a standard for translating from space to space. The fatal flaw is that by definition, we have no access to that mythical color save through a, you guess it, device. So it becomes an act of faith, not science, to talk about accurate color. It's all a compromise, a quest for pleasing color. There is no other. The only question is who you please, and usually that's the guy that signs the check.

rutt

Jul-04-2007, 09:24 AM

There's no such thing as an impossible color when defined in LAB, it defines (with some holes) human vision based on its daddy, CIEXYZ.

Let's put this aside for the purposes of this discussion. It only bears on the definition of the word "impossible". We can quibble, but it's a digression.

We've talked about describing a cast using the original RGB working space and the fact that, lots of images need a color cast.

Agreed. I have lots of images like this. Most recently:

http://colortheory.smugmug.com/photos/153965064-L.jpg
The Queen of the Dammed (actually Willis), Boston Ballet's 2007 production of Giselle, Kathleen Breen Combes

Also mixed casts, such as:

http://rutt.smugmug.com/photos/69321630-L.jpg
Balanchine's Serenade, Boston Ballet, 2006

Its quick and easy to simply LOOK at the image in context, something I've discussed, then fiddle around looking at LAB numbers that tell you that the image you like is wrong. I'd frankly be looking at the source color space numbers (in my case, ProPhoto RGB).

I would submit that all wedding dress images should not be neutral while some should be, but it seems easy just to look at the image and make the decision.

If you're asking me if the first thing I recommend you do is mouse around an image and look for odd color values, my answer would be no. I' look at the entire image first and see if I think it needs work or not. Much of this work BTW would take place in my raw converter (or going back in time, on my film scanner).

Your eyes must be much better than mine (and many others.) Lots (and I do mean LOTS) of times I don't see it. Once I measure, I know there is a cast of some sort and then make a decision about what to do about it. I don't always neutralize the cast (see the images above.) But after measuring I'm aware of it. And often, the at least partially neutralizing the cast does make an improvement which everyone prefers.

Here are some examples of this phenomenon:

http://dgrin.com/showthread.php?t=60157
http://dgrin.com/showthread.php?p=522426#post522426
Here is one where I didn't measure my own image and was glad that someone else did: http://dgrin.com/showpost.php?p=522093&postcount=17
Another case where I should have measured: http://dgrin.com/showpost.php?p=180164&postcount=2

There are many more, some of which happened via private emails. Try searching for my posts containing the word "cast".

rutt

Jul-04-2007, 10:03 AM

Edgework is better at measuring and figuring out what to do that I am. Here are some examples where he did this:

http://www.dgrin.com/showpost.php?p=184160&postcount=15
http://www.dgrin.com/showpost.php?p=190439&postcount=6 (he caught me here.)

arodney

Jul-04-2007, 12:36 PM

Andrew—your knowledge and credentials are obvious and need no qualification, but forgive me if I say that you sound like you're all strategy and no tactics. Anyone who can acknowledge that "accurate color" will, nonetheless, be ugly color that pleases no one, yet not realize that the argument is essentially meaningless beyond that point, is mistaking theory for results.

OK let me try again to see if I can make this clear.

There’s only one way to really define accurate color just as there’s only one way to define accurate distance, speed etc. You measure it. Anything else is someone’s interpretation of accuracy and all we can do is agree or disagree. There’s no way to say “but this is the measured color of what you placed in front of the camera”. If I measure the color, illuminant and dynamic range of a scene AND I send those numbers to your output device (a display) it not only doesn’t look like what you saw but looks pretty ugly. That is due to the issues known as the reference medium. Your display has a fixed gamut, contrast ratio and expects output, not scene referred colorimetry. The ICC paper spells this out, it was co written by a color scientist. If you want to take up the issue that accurate scene colorimetry doesn’t look correct output referred on the device (using this fellows examples), you two can debate this. And you can debate the earth is flat or the moon is made of cheese. Scientific analysis would prove you wrong.

Pleasing color is the color on some output device that you, or I or anyone likes. We can’t measure that and compare it to the scene to gauge accuracy because the reference media is totally different, as are a host of other factors. You can say that this display or print is showing you the color exactly as you recall seeing it but there’s no way to measure or gauge if what you believe to be true is or isn’t. So thus far, the debate, if there is one, is that using the term accurate color is bested reserved for describing the color of the scene and pleasing color is bested reserved for describing the numbers you produce when you get the color appearance you desire. If you want to call that accurate, OK but I think its sloppy and it doesn’t allow anyone any way to gauge if this is the case or not. If you like huge fudge factors in describing what it is you’re doing with a big pile of numbers on a computer, so be it.

We send all kinds of different numbers to devices in an attempt to produce matching color appearance and thanks to metameric matches, this is achieved every day.

I've been producing color for magazine covers, photospreads, photographers and web sites, for nearly 20 years, and doing it well. I've plied my craft in shops that spit on the notion of color management, and I've done it in shops that worship the concept like it was the salvation of western civilization. I'm curently working in an environment that typifies most such environments: they pay lip service to the idea but really don't do it well.

And your point is what in reference to the discussion?

When we acquired a new proofing system a while back, our production wizard ordered up a proof from our old provider to compare with ours. Shock of shocks, they didn't match. So he emarked on a city wide quest, ordering contract proofs from about a dozen different services. All were different. There's nothing more pathetic than a so-called production wizard staring at a pile of proofs that don't match and wailing "Which one is correct?" I told him "The one with the client's initials in the lower right corner, the one a printer contracts to match on press. That's your correct color." That's tactics.

Other than what you say doesn’t surprise me in the least, again, what’s your point in the context of the current discussion? If you want to discuss the need for output specific standards like G7 or TR001 in the print industry I’m ready. If you want to admit that process control and press standards are not well implemented in the US, I’m with you and find the above comments about your proofing experiences in line with mine.

Rutt makes a passionate case for Dan Margulis' approach, by the numbers, you make a passionate case for dismissing Rutt's case, also based on numbers... numbers, schmumbers.

No I didn’t say that and in fact discussed where using numbers IS important and useful! But the question becomes, what numbers, based on what and to accomplish what?

What we have here are photographers looking for tactics and theory be damned. Personally, I don't believe you fail to understand the point Rutt made in his last post; you're too smart. Talk all you want about this space or that profile, in the real world, when you need results, taking a look at the numbers and noting some general patterns about relationships between the different channels, is not only warranted, to refuse to do so is amateurish and to deny the usefulness ceases to be an artistic, or scientific, argument, and becomes mere politics.

Is someone attacking you because again, your above point doesn’t make any sense in the context of the discussion.

The myth of color management rests on the notion that there exists, somewhere, a device independent definition of color from which all others can be measured, and which can serve as a standard for translating from space to space. The fatal flaw is that by definition, we have no access to that mythical color save through a, you guess it, device. So it becomes an act of faith, not science, to talk about accurate color. It's all a compromise, a quest for pleasing color. There is no other. The only question is who you please, and usually that's the guy that signs the check.

First, what basis do you apply to call this a myth? 2nd, the color model Dan now loves over CMYK, LAB IS based on human vision and the numbers define color appearance based on human perception WHEN talking about single patches of color (NOT color in context since there are no color appearance models at work here. If there were, the two patches in the optical illusion I illustrated would be accounted for). There does exist several device independent mathematically created spaces that define all colors humans can see. You can measure the colors and produce these values in a very non ambiguous way, just as you can use your speedometer in your car to gauge how fast you are moving. And I don’t know who has said this is an act of faith, other than you above. So again, most of your points are lost on me because I think you are trying to defend someone else or some other belief system but you’re not thus far doing so with anything other than emotion.

Other than apparently defending Rutt (who needs no defending) or Dan (who does), what’s your point, what’s on your mind?

rutt

Jul-04-2007, 01:11 PM

No I didn’t say that and in fact discussed where using numbers IS important and useful! But the question becomes, what numbers, based on what and to accomplish what?

I guess I missed that. Measuring for neutrality? Or something else?

The measurements I make are not very fine at all. I mean that I don't pay that much attention to the exact numbers, only to some gross relationships. I find LAB measurements convenient because it's easy for me to see if something is green or blue instead of magenta or yellow (for example). Neutrality stands out to me because it's 0. I can tell if flesh is more magenta than yellow at a glance. No big deal. I'm sure I could learn to do this in RGB or CMYK or whatever. It just happens that I find the LAB numbers easy to use. So that is the answer to the questions what numbers.

As to what I want to accomplish with these numbers, it's detecting casts which when corrected will represent an improvement. I have some theories about when this is, but as I said before, this thread is about your ideas, not mine or Dan's or anyone else's (at least that's my goal.) I've learned that by doing this kind of measuring I can often detect the possibility of such an improvement when I wouldn't have done so otherwise.

So for me this is the single biggest question for you. Do you never do this and just trust your eyes and good color management all the time? If so, did you have to train yourself somehow to see what I don't seem to be able to see? Do you think I can learn it?

arodney

Jul-04-2007, 01:31 PM

I guess I missed that. Measuring for neutrality? Or something else?

Neutrality, black and white clipping, saturation clipping of all colors.

I find LAB measurements convenient because it's easy for me to see if something is green or blue instead of magenta or yellow (for example). Neutrality stands out to me because it's 0.

A cousin of LAB and a much easier scale to use is based on LCH which I wish Adobe would add to the info palette. Chroma is where you'd look for neutrality (zero is neutral, 100 fully saturated). Its the aStar and bStar portions of LAB which are not at all intuitive but with LCH, color is defined using H for Hue (zero to 360, makes sense when you look at a hue wheel).

It is a lot easier to initially spot the degree of neutrality with a single value but again, in all RGB working spaces, neutral is R=G=B.

I can tell if flesh is more magenta than yellow at a glance. No big deal. I'm sure I could learn to do this in RGB or CMYK or whatever. It just happens that I find the LAB numbers easy to use. So that is the answer to the questions what numbers.

The method you're using is sound, the color space isn't really (my original point in the other forum post that started all this). CMYK is a very specific output color space, the numbers can vastly change from one space to the other. LAB makes MUCH more sense in this respect. Its based on human color vision and its self defining unlike RGB (with RGB, you can't provide numbers without an associated color space which is the same with CMYK).

So for me this is the single biggest question for you. Do you never do this and just trust your eyes and good color management all the time? If so, did you have to train yourself somehow to see what I don't seem to be able to see? Do you think I can learn it?

I use numbers yes but I use what I see first and foremost because again, you're really just getting numeric values of one or a group of solid colors and very often, you're not getting the colors in context with the rest of the image which is important. So, knowing the values I clip shadows and highlights is useful, I don't always want to clip that data (sometimes I do). Knowing that a color is maxed out in saturation is useful. If I'm looking at skin tone, I want to see that part of the image in context with all the thousands of other similar and dissimilar colored pixels.

Ultimately the proof is in the print but I'd like to see that color appearance on screen before I click the Print button. If a lot of my work was solid colors (pie charts), working BTN would be far more effective but like the example of the cement and building shot at night, simply color correcting because you're produced a neutral isn't effective.

Try this, use the Set neutral (WB) eyedroppers in ACR, LR or Photoshop. Every hunted around, clicking and finding you didn't like the overall color? Yet every time you clicked, you did produce a neutral. The key is having an image where the neutrals should indeed be neutral (that's not going to fly on a sunset image). So its not just clicking on the right pixels to define a neutral, its looking at the entire image and deciding if the correction works for you or doesn't (again, neutral or case, neither is accurate but the right answer IS pleasing).

Duffy Pratt

Jul-04-2007, 01:40 PM

arodney

Jul-04-2007, 02:07 PM

Actually, for the Lab = 0,0,128, Dan uses the term "imaginary," instead of "impossible." For Dan, and I think for what you are talking about here, an impossible color is one that can be displayed, but does not actually occur anywhere under white light: examples are blue fur, green skin, purple grass, yellow skies, red Union army uniforms, etc... In this sense, impossible is something that falls on the extreme end of implausibility.

Duffy

Imaginary, impossible, what's he trying to say here?

Displayed can be output; the gamut of our displays is roughly sRGB in size, pretty small. And what output device is he referring to? CMYK SWOP ink on paper? Every output device on the planet? Implausible based on who's critera? Its a silly term he made up that doesn't mean anything.

I have seen images of blue fur and green skin (how about those crazy kids at Football games or someone on stage?). The entire concept is asinine.

jfriend

Jul-04-2007, 02:21 PM

Imaginary, impossible, what's he trying to say here?

Displayed can be output; the gamut of our displays is roughly sRGB in size, pretty small. And what output device is he referring to? CMYK SWOP ink on paper? Every output device on the planet? Implausible based on who's critera? Its a silly term he made up that doesn't mean anything.

I have seen images of blue fur and green skin (how about those crazy kids at Football games or someone on stage?). The entire concept is asinine.

I've been standing on the sidelines here, but this is just melarkey. The concept of colors that don't occur naturally in nature (we're not talking about crazy kids with green paint on their faces, we're talking about natural skin color or natural fur color) is a real and useful concept to understand and know how to use. I personally find it useful and it can definitely help identify subtle color casts in many contexts and give you more specific direction for how to remove it.

You can say you don't personally find it useful, but many do, so calling the entire concept asinine is just showing how irrational you are being and these extreme positions about anything Margulis says are distracting from the times when you do have a useful point to make.

I know this concept is useful to me so I'm not going to bother to argue that with you. If you want to offer something better to replace it with that isn't just looking at the image with my eyes, I am open to new and improved ways of doing things.

arodney

Jul-04-2007, 02:37 PM

The concept of colors that don't occur naturally in nature (we're not talking about crazy kids with green paint on their faces, we're talking about natural skin color or natural fur color) is a real and useful concept to understand and know how to use.

What's asinine is making up a term like impossible color when in fact, the color is real, can be captured, measured, defined numerically and output. Lots of these colors are natural. What's asinine is making up a term that doesn't mean anything, isn't at all well defined.

Think about the term. Impossible color. Well there are wavelets of light that fall outside human vision. I can't see anything beyond the 700nm or below say 400nm so OK, those are invisible, impossible colors that maybe a dog or fish can see. Again, its real easy to make up this stuff so you sound important, but explain what you're saying here. A color I CAN capture is impossible? Prove it. And what makes the term (which really sounds totally bogus to me) important?

You can say you don't personally find it useful, but many do, so calling the entire concept asinine is just showing how irrational you are being and these extreme positions about anything Margulis says are distracting from the times when you do have a useful point to make.

Wow, lets be clear, what's asinine is the term as described to me. I didn't say the entire concept is asinine.

I know this concept is useful to me so I'm not going to bother to argue that with you.

OK so define what is an impossible color that can be defined using our 24-bit systems and how calling this color impossible is useful.

arodney

Jul-04-2007, 02:45 PM

How many impossible colors do you see here?

http://www.peteturner.com/Classics/index.html

At what numeric value (that's all Photoshop and computers can work with) does a impossible color become possible?

How many impossible colors can dance on the head of a pin?

How is making up terms that have such wiggle room help us?

Duffy Pratt

Jul-04-2007, 03:04 PM

As Dan uses it, the term "impossible color" doesn't refer to the color itself. The term is a shorthand, and within Dan's writings, its something of a piece of jargon. It's a way of speaking when doing his kind of color correction.

You may not like the term. But many, many people both understand what he is talking about and find it useful. As such, the idea behind the term is both meaningful and useful (to many), no matter how asinine you think it sounds. (BTW, I think the term "output-referred" sounds at least as awful, but since I understand what you mean by it, I won't object too hard to your use of it, even though I would never ever use the term myself.)

I also have a hard time believing that you don't understand the idea behind the term. If someone shows you a picture of a strawberry, and its stronger in the A channel than the B channel, that's a clue that there's something wrong. If it shows negative in the B channel, then there's something even further amiss. Strawberries aren't purple. I realize that's not a scientific statement, but I think its meaningful and something that most people can understand and use.

Now go to Rutt's question. What happens when many people's eyes don't spot these anomolies? That does happen -- I've seen it again and again on various forums. People think colors look just fine. Then someone plays with the pictures, finds that something was off, and fixes it based on the discovery. It's not uncommon for everyone to then agree that the picture is now better. With your approach, how would you make this sort of improvement?

Duffy

Duffy Pratt

Jul-04-2007, 03:09 PM

How many impossible colors do you see here?

http://www.peteturner.com/Classics/index.html

Honestly, the blues to the left of center are bluer than any sky I have ever seen. I'm not sure I would say that they are impossible (in Dan's sense) but they are certainly implausible. I look at a picture like that as having highly exaggerated colors, at least in the skies. More to the point, I think people might agree or disagree with me, but it would be a rare bird who would say "exaggerated colors? I have absolutely no idea what you are talking about."

Duffy

rutt

Jul-04-2007, 03:48 PM

The method you're using is sound, the color space isn't really (my original point in the other forum post that started all this). CMYK is a very specific output color space, the numbers can vastly change from one space to the other. LAB makes MUCH more sense in this respect. Its based on human color vision and its self defining unlike RGB (with RGB, you can't provide numbers without an associated color space which is the same with CMYK).

I must not have been clear. I use LAB not CMYK for this.

Try this, use the Set neutral (WB) eyedroppers in ACR, LR or Photoshop. Every hunted around, clicking and finding you didn't like the overall color? Yet every time you clicked, you did produce a neutral. The key is having an image where the neutrals should indeed be neutral (that's not going to fly on a sunset image). So its not just clicking on the right pixels to define a neutral, its looking at the entire image and deciding if the correction works for you or doesn't (again, neutral or case, neither is accurate but the right answer IS pleasing).

Yes, I do this all the time to try to find a good starting point. For the ballet shots, I can even talk to the lighting director to find out the color temperature of the lights he uses. But these days I find that I can do more with flesh tones, skies, snow, fur, water, &etc than with neutrals. When there really are neutrals, it's often the best clue, but if it leads to bad skin tones, then I won't use it.

The second ballet shot (the one with many dancers) is a good example. The dresses are white but the light is very blue. Neutralize the white dresses and the flesh tones are very wrong. Look at it carefully and you'll see the blue light on the faces. What I did was to get some places on the flesh that had A<=B in LAB and the rest looked right. You could see the blue light but also see that the faces were healthy flesh tones. The dresses ended up blue. Looked like what I saw. But I don't think that I (as opposed to someone else) could have done this without measuring and thinking about how it was all supposed to work together. Much more complicated than just setting the WB to make the known neutral dresses neutral.

Is this very different from what you would have done?

arodney

Jul-04-2007, 04:07 PM

As Dan uses it, the term "impossible color" doesn't refer to the color itself. The term is a shorthand, and within Dan's writings, its something of a piece of jargon. It's a way of speaking when doing his kind of color correction.

I've decided that I too should make up terms about color!

Universal color. This is color contained within our universe. Note that you should find out the exact boundaries of our universe as being off a light year here or there doesn't cut it.

Half color. This is color you see when only one eye is open. Try alternating your open and closed eye, do the colors look different?

Vegetable color. Everyone knows what Tomato red looks like right? Or Avocado green. Little reason to measure the color or use a color space and numbers, when we use a vegetable color, everyone knows what we're looking at and seeing.

You may not like the term. But many, many people both understand what he is talking about and find it useful. As such, the idea behind the term is both meaningful and useful (to many), no matter how asinine you think it sounds.

I hope you find my new terms useful too in describing color!

(BTW, I think the term "output-referred" sounds at least as awful, but since I understand what you mean by it, I won't object too hard to your use of it, even though I would never ever use the term myself.)

It doesn't have a nice ring to it, I'd agree. However, ask any color scientist or engineer working in imaging if they know the term and they will. Please Google Output referred then Impossible Color and tell me what you find and referenced where. The ICC, a body of manufacturers and color scientists use the term all over their site when discussing the terms I've attempted to explain here.

I'm not a big fan of Perceptual Rendering but that's what the name is for this gamut compression algorithm. I don't really care for Unsharp Mask, so many people are confused by the Unsharp part but, the term has roots in analog photography and is used as such.

I also have a hard time believing that you don't understand the idea behind the term. If someone shows you a picture of a strawberry, and its stronger in the A channel than the B channel, that's a clue that there's something wrong.

Why don't I just look at it? And what makes this color impossible, clearly it IS possible. Why not say its got a color cast or doesn't look like a strawberry?

If it shows negative in the B channel, then there's something even further amiss. Strawberries aren't purple. I realize that's not a scientific statement, but I think its meaningful and something that most people can understand and use.

No its not and worse, its got an enormous fudge factor since its totally undefined. So what LAB values automatically ensure the color is possible and then not possible?

Now go to Rutt's question. What happens when many people's eyes don't spot these anomolies? That does happen -- I've seen it again and again on various forums.

Is this like the tree falling in the forest when no one is around?

Seriously. You're suggesting that some users see their images and don't find a problem but others do, fix it and original user is amazed. OK, that's useful I guess if we want to edit colors by committee. But it again, doesn't tell us very much about the user. What system did they have, was it calibrated? Did they look at the image and like it, only to find an edit done elsewhere was more pleasing? Was the user happy with every edit? Did it match the original?

People think colors look just fine. Then someone plays with the pictures, finds that something was off, and fixes it based on the discovery. It's not uncommon for everyone to then agree that the picture is now better. With your approach, how would you make this sort of improvement?
Duffy

Nothing you said here is something I'd disagree with. Clearly people find they prefer the color appearance of some images after others mess with them.

I would submit that the first thing to do IS teach them numbers (highlight, shadow, neutrality if necessary and desired), along with a display that produces a reasonably correct preview of the numbers.

I actually submitted an image I shot to the Color Theory list and had others mess with it. But this wasn't a simple bride in a dress or something illuminated under some standard appearing conditions. I submitted the image because its all about interpreting the image, much like the work of Pete Turner (by all means, lay the info palette over his stuff). And to be honest, I didn't like any of the renderings (all done from raw) as much as mine simply because this was a very unusual image of which there are many possible color options (if you want to see the shot, its the fourth on this web gallery: http://digitaldog.net/ARsAmazonPicks/ ). Now some of the renderings were quite interesting and obviously the person making the renderings preferred it.

There's a LOT of interpretation in this game. Numbers only work so well in so many cases. But I'm not dismissing their use. I do question using a CMYK output color space for generating the numbers. I do question making up terms for the club which outside make no practical sense. I mean, impossible colors? How about wrong? No, it doesn't sound sexy but it makes sense. I do question using the term accurate to describe something that can't be measured so this so called accuracy can be defined. You say this color is accurate, I say it isn't. How do we rectify this debate? Well we could actually measure the darn colors.

IF the color numbers you have produce the color on output you desire, OK, that's accurate to a degree but we can't measure this because I can assure you, the color numbers that produced the print you like are absolutely not the same colors you had in front of your camera.

Semantics? Maybe, but good teachers attempt to define terms that have little if any wiggle room should someone question what on earth they are trying to teach you. Making up terms, like Vegetable color might actually get some attention my way, but its not worth it because the term as I'm sure most of you would agree, is silly.

To end this (I really do want to go out and enjoy the 4th) let me leave you with an old Chinese proverb, which says: The first step towards genius is calling things by their proper name.

arodney

Jul-04-2007, 04:12 PM

I must not have been clear. I use LAB not CMYK for this.
Is this very different from what you would have done?

Not really. The interesting bit is when you say you neutralized the dress and the skin was wrong. Wrong visually and/or numerically? IOW, if all is well, both back up your opinion of this rendering. It also shows that BTN (using in this case neutral color on the dress) is just dead wrong. But the dress is white! But it looks wrong.

LiquidAir

Jul-04-2007, 05:38 PM

I am a bit puzzled. There are two possible goals to image processing: making an accurate reproduction and making a pleasing image. If you want an accurate reproduction, you start with a reference light source and a calibrated camera. If you didn't do that, creating an accurate reproduction is likely a fools errand.

The premise behind trying to make a white dress shot under a blue light be white by the numbers is rooted in trying to create an accurate reproduction of the dress. Is that really what you want to achieve? Trying to get an accurate reproduction of a scene shot under anything other than very simple color black body spectrum lights is fraught with peril. The real interaction between light and materials requires modelling the full spectrum, not just the R, G and B channel you capture in a camera. As a result, the color shifts under gelled lights is likely to not be simply represented in terms of any of the common methods for adjusting images.

In my personal experience, I find correcting by the numbers to be most useful when shooting with studio lights or in sunlight. Standard color balancing tools work really quite well there because the lights are well enough behaved that a resonably accurate reproduction is possible and generally in those cases I find that that it is easiest to create a pleasing image by starting with an accurate reproduction.

However, when shooting in mixed or complicated light, I often find that the best route to a pleasing image is to acknowlege the colored and deliberately leave the cast in. A scene shot next to a small incandescent bulb can look better with a orange cast because the viewer knows the light is colored. Similarly, the viewer knows that the lights on stage are colored, so leaving a white dress blue is completely reasonable. Beyond that, by leaving the cast on the dress you give your viewers a hint about the color of the light which can change their expectations about the colors in the rest of the image. So, on a stage lit with blue light the skin tone that creates the most pleasing photograph may in fact have a negative LAB b channel despite the fact that would be completely wrong if you were trying to create a reproduction.

Duffy Pratt

Jul-04-2007, 05:51 PM

rutt

Jul-04-2007, 06:03 PM

Not really. The interesting bit is when you say you neutralized the dress and the skin was wrong. Wrong visually and/or numerically? IOW, if all is well, both back up your opinion of this rendering. It also shows that BTN (using in this case neutral color on the dress) is just dead wrong. But the dress is white! But it looks wrong.

Neutralize the white gauze of the dresses and the flesh is way too yellow. Both BTN and to anyone's eye, I'm pretty sure. It's not at all subtle.

http://rutt.smugmug.com/photos/169607028-M.jpg

This is an unusual shot, even for theater light. Usually the lighting director doesn't want an obvious cast like this any more than a portrait or wedding photographer. But this is a famous ballet and the blue light has come to be a part of its presentation. Do the blue dresses actually look wrong to you, or do you just mean that they are wrong in that we know they are white and so some theory which neither of us agrees with dictates that we should neutralize the cast?

I don't believe we should always make known neutrals neutral or all flesh more yellow than magenta (as this shot shows.) But I think it's important (at least for me) to know when this isn't true and understand why not. Particularly flesh, vegetation, skies, hair, and fur need either to measure reasonable colors or I need to know why not. In my experience, it's the very rare shot which can stand to have these things wrong everywhere. (In this shot the flesh measures roughly right in at least some places and that was what I used as a guide. In the Giselle shot, everything is "wrong" BTN everywhere, but the light was very blue and very dark and the dancer is supposed to be dead.)

edgework

Jul-05-2007, 05:38 AM

OK let me try again to see if I can make this clear.Rest easy. It's quite clear. I'll reaffirm my respect for your knowledge and the world you inhabit.

The ICC paper spells this out, it was co written by a color scientist. If you want to take up the issue that accurate scene colorimetry doesn’t look correct output referred on the device (using this fellows examples), you two can debate this. And you can debate the earth is flat or the moon is made of cheese. Scientific analysis would prove you wrong.

No thank you. I have no interest in debating a color scientist about anything, possessing, as I do, a clear grasp of my knowledge and its limitations. Besides, that's not my world. It's your world and we don't live in the same place. My world is the world of deadlines and cranky clients. And my industry, my refererences to which you dismiss as not being to the point, has been, and remains, the place where the greatest effort has been made to translate the world of color labs and scientific papers into a workflow that will meet deadlines and satisfy cranky clients. Theoretical perfection notwithstanding, the results have been, and continue to be, checkered at best.

I've been your lab rat, Andrew. I've been there on the front lines while you guys have tested your theories and patiently explained to us "color operators" (not to be confused with color scientists, certainly), that the "theory is perfect, it's the implementation that's flawed," much like my old college professor used to say about Marxism. But however well or poorly the effort at color management is implemented, for me, the result remains the same: I'm standing at a light box studying an imperfect proof, trying to plot a strategy that will satisfy the client. That the imperfection of those proofs should be, theoretically, impossible, doesn't help me much when, despite an entire department dedicated to calibration and color management, they still come out wrong. The situation is exactly the same for a photographer studying an imperfect shot, trying to plot a strategy that will satisfy the client, even though, as is often the case with photographers, the client is themselves.

Which brings me to the real confusion that I have with your posts: why the continual, unrelenting condescension, scorn and ridicule you direct at Dan Margulis and his techniques?

Other than apparently defending Rutt (who needs no defending) or Dan (who does), what’s your point, what’s on your mind?

The point is that people read Dan's books and the quality of their images improves, they make money, clients go away happy. This is an immediate result, predictable and repeatable. When I'm plotting that strategy to please a client, I'm not going to call on a color scientist with a couple of profiles in his back pocket and a handful of calibration devices; I'm going to recall some basic techniques that I and color providers everywhere recognize as useful means to getting a desired result.

I don't doubt that there is a solid theoretical basis for considering this "beside the point." I'm sure if I study this thread again, in detail, I could begin to quote that theoretical basis. But in the world of deadlines and clients, that's all, well... beside the point.

arodney

Jul-05-2007, 06:28 AM

The more I read what you are saying, the more it sounds like there is such a thing as "accurate" color and there is such a thing as "pleasing" color. Accuracy, as far as you are concerned, must be measurable by some instrument. What makes something pleasing, however, has a big fudge factor and is largely subjective.

In a nutshell yes only because there's no measurable matrix for pleasing color. There is for accurate color.

Because it is subjective, you think its hopeless to give any advice about how someone can go about making a photograph more pleasing (I may be overstating, but this is the impression I get).

Yes that's overstating it. Obviously there are many tools and techniques in raw converters and Photoshop to produce pleasing color even using numbers. But numbers are not the holy grail especially when based on an output color space like some CMYK device UNLESS you know, based on sending numbers to that device and examining the actual printed color. The origin of all this started in another post where I questioned using a set of CMYK values in an article for pinning skin tone and discussed the basis of such numbers on a very specific printing condition.

The best you think anyone can do is say: use your eyes, and there can be no better or worse in the realm of what's pleasing because it what's better can't be nailed down exactly by some instrument.

Use your eyes first, use numbers as well when they provide useful analysis of the pixels based on the correct color space. I've said several times (and its in print all over the web, in print and in my book), using your eyes on a calibrated profiled display in a color managed application WITH the proper feedback of numbers gives you the best of both worlds.

pathfinder

Jul-05-2007, 08:59 AM

In a nutshell yes only because there's no measurable matrix for pleasing color. There is for accurate color.

Yes that's overstating it. Obviously there are many tools and techniques in raw converters and Photoshop to produce pleasing color even using numbers. But numbers are not the holy grail especially when based on an output color space like some CMYK device UNLESS you know, based on sending numbers to that device and examining the actual printed color. The origin of all this started in another post where I questioned using a set of CMYK values in an article for pinning skin tone and discussed the basis of such numbers on a very specific printing condition.

Use your eyes first, use numbers as well when they provide useful analysis of the pixels based on the correct color space. I've said several times (and its in print all over the web, in print and in my book), using your eyes on a calibrated profiled display in a color managed application WITH the proper feedback of numbers gives you the best of both worlds.
Andrew, much of the folks here on dgrin do use the CMYK (http://smugmug.com/help/skin-tone) values from Baldy's Blog ( one of the co-founders/owners of Smugmg). These CMYK values (http://smugmug.com/help/display-color) are not abstract values but ones taken from prints ordered via Smugmug and printed via EZPrints. There is an ICC profile available so that one can preview the appearance of the image in Photoshop. The link for the ICC profile is about 3/4s of the way down the second link I listed above.

rutt

Jul-05-2007, 09:12 AM

Use your eyes first, use numbers as well when they provide useful analysis of the pixels based on the correct color space. I've said several times (and its in print all over the web, in print and in my book), using your eyes on a calibrated profiled display in a color managed application WITH the proper feedback of numbers gives you the best of both worlds.

Is this a fair summary of your philosophy for photo improvement? Is there more? Does it inform some specific techniques we can learn to employ? Examples? (Illustrated step-by-step examples of techniques are always much appreciated here on digrin.)

Oh, and it seems that you do think my use of LAB numbers to look for evidence of casts is appropriate ("proper" in your words.) True?

arodney

Jul-05-2007, 09:35 AM

Andrew, much of the folks here on dgrin do use the CMYK (http://smugmug.com/help/skin-tone) values from Baldy's Blog ( one of the co-founders/owners of Smugmg). These CMYK values (http://smugmug.com/help/display-color) are not abstract values but ones taken from prints ordered via Smugmug and printed via EZPrints. There is an ICC profile available so that one can preview the appearance of the image in Photoshop. The link for the ICC profile is about 3/4s of the way down the second link I listed above.

I just checked the ICC profile, its RGB, made using the TC918 RGB target in ProfileMaker Pro (the product I use). So maybe the link is incorrect?

Why would you use an ICC RGB output profile for print, and use a CMYK profile for numbers when the two are not even close being equal.

The CMYK part is still quite odd to my thinking.

arodney

Jul-05-2007, 10:12 AM

Is this a fair summary of your philosophy for photo improvement? Is there more? Does it inform some specific techniques we can learn to employ? Examples? (Illustrated step-by-step examples of techniques are always much appreciated here on digrin.)

Oh, and it seems that you do think my use of LAB numbers to look for evidence of casts is appropriate ("proper" in your words.) True?

First, yes. But I'd quickly dismiss the numbers if I didn't care for the preview!

My philosophy, if you can call it that (which seems to put far too much emphasis on me) is based on work done since Photoshop 1.0 shipped, working with some pretty good photographers and experts (the top of my list would be Bruce Fraser who I've knew from the early 90's) along with Jeff Schewe, Mac Holbert (Nash Editions), JP Caponigro, as well as regular work with the authors of Photoshop (Thomas Knoll, Mark Hamburg).

In a nutshell, capture as much data as possible (high bit, wide gamut). Edit in such conditions and send as much data as possible to an output device using good color management practices. Whenever possible, work on layers, leave the original data untouched, produce color and tone correction early on (in scanner or raw converter), doing the biggest corrections first in the order specified (when mandated, ACR and LR have a recommended top down, left to right processing order). Soft proof and edit if necessary based on that for the output device and make as few proofs as possible to save time and money. Numbers are useful in some cases, early on but color appearance is more useful as viewing color in context within an image.

Also, one problem I read on the color theory list is this idea that the raw module should be set at some flat, default and that you should then use Photoshop to 'correct' the image. I think this is based on the mindset that if all you know how to use is a hammer, everything looks like a nail. With raw data, you're simply working with a very different kind of information than using Photoshop on a rendered image. Its a real bad idea to think of Photoshop as a post raw conversion correction tool for a lot of reasons (how the raw data is encoded, the fact that raw rendering is the only true non destructive means of editing since the original data is untouched, the use of metadata instructions, the way the various tools are applied to linear encoded data as opposed to gamma corrected baked color pixels). Photoshop is a fine pixel polisher. It's always been a 'one image at a time' process.

Lastly, test, test test! Don't take anyone's word for a technique that is necessary better. More complex processes isn't necessarily better but it often makes the user seem macho. There's the right way and the best way to process images. Sometimes, the best way doesn't allow you to get the job done in time even though the final data may be less pristine. For example, doing all kinds of multiple complex operations on 500 images of widgets on a white bkgnd might indeed produce slight quality benefits but if you can only process 200 of them within your time budget, it doesn't really matter. So I handle production work a bit differently than personal portfolio work; I will handle 500 2x2 images going off to a catalog differently than a 30x40 print I plan to output on my 4800.

Perfect example is picking a rendering intent for output. I ask my students what is the best rendering intent to us for color conversions to print. Some say Perceptual, some say Relative Colorimetric. The right answer is the one that produces the best color rendering that you prefer. Numbers can't help you here! ICC profiles don't know anything about images, only devices. So the best workflow would be to toggle the options using the Convert to Profile command or in the custom Soft Proof. If you have one image, no big deal, if you have 500, it takes far too long to look at each. Try one or two, pick one intent, build an action or other automation process to convert the other 499 images and be done.

Another example. For years, people have been told to convert a file to LAB to sharpen the L channel. Well that takes time and causes more data loss than just using USM and the Fade Luminosity option plus you also have the opacity slider. Are the mathematically identical? No, one tosses more data in the process but the end result is avoiding color fringing from the sharpening thanks to using the Luminosity blend mode. Better, Faster, Cheaper: pick any two.

Duffy Pratt

Jul-05-2007, 10:23 AM

When dealing with what makes a "good" skin tone, we are almost necessarily in an area where there is a huge fudge factor -- lots of room for disagreement. The reason for CMYK numbers is because people find them helpful and easy to understand.

I often use CMYK numbers (in the PS info palette) as a guide when editing skin tones in an RGB working space. I've tried to get some kind of easy handle on the RGB relationships that you could use as a rule of thumb for skin, and it I just haven't been able to. My web searches don't reveal anyone else who has found these relationships either.

So the basic reason for using CMYK numbers is because its easy, understandable, and it works given the pretty broad leeway there is for skin in the first place. To get me to switch to some other process, I'd need some pretty clear proof that it a) got me better results and/or b) saved time. So far, I haven't been shown any such approach using RGB numbers for skin.

Duffy

arodney

Jul-05-2007, 10:49 AM

When dealing with what makes a "good" skin tone, we are almost necessarily in an area where there is a huge fudge factor -- lots of room for disagreement. The reason for CMYK numbers is because people find them helpful and easy to understand.

Just as many find them difficult to understand. A lot depends on where you come from and what you are initially taught. Most photographers I work with don't 'get' CMYK at all and understand RGB. And forget CMYK numbers in many comon raw converters.

I often use CMYK numbers (in the PS info palette) as a guide when editing skin tones in an RGB working space. I've tried to get some kind of easy handle on the RGB relationships that you could use as a rule of thumb for skin, and it I just haven't been able to.

Why not just reference the RGB numbers in the info palette when over skin you know produces a desired color appearance? Now its based on the actual color space. Plus, once again, if for any reason, the CMYK color settings are not as originally set, the values are off. But the RGB numbers are what the actual pixels represent, not some conversion from those number (my basic beef using CMYK).

In a way, its like having someone speak English, having a translation into French and then back into English. Why the translation?

Duffy Pratt

Jul-05-2007, 11:02 AM

Why not just reference the RGB numbers in the info palette when over skin you know produces a desired color appearance? Now its based on the actual color space.

To do this I would have to develop a series of samples. I'm not sure how many I would need, but lets say 5-6 basic skin types (at a minimum), with at least 4 different exposure ranges for each. So, lets say conservatively I end up with 20 samples. Now I would have to open the appropriate file for comparison. To me that sounds like alot of extra time, although I could imagine getting quick at the process. Now, if someone showed me how this process regularly produced better results, then I would do it.

Right now, to see whether this got better results would involve lots of testing by me. In principle I am not oppossed to doing that sort of testing, but my time can still be better spent learning other things, since I already have a system that's doing alright for skin tones for most pictures.

Duffy

DavidTO

Jul-05-2007, 11:14 AM

Why the translation?

Because for skin tones CMYK and LAB both provide an understandable relationship that can provide an important guideline as to whether you're on target or not. I've never found an RGB equivalent. If you can provide me with one, I'd be ecstatic. But so far, only CMYK and LAB can do this. I know that Y should be a few point greater than M, and that C should be a fraction of either of them. Or, in LAB, I know that B should be more than A. They're not hard and fast rules, but it's a great aid in making sure that your skin tones are correct. And this cannot be replicated in RGB.

The difference is akin to what happened when people finally admitted that the earth circled the sun, instead of being the center of the universe. All calculations became easier and the heavens more understandable.

Duffy Pratt

Jul-05-2007, 11:19 AM

I've got a few questions on your "philosophy" summary, which I thought was both clear and interesting.

You say to capture as much data as possible. One might conclude from this that more megapixels is always better, because more pixels means more data. It's pretty clear that that is not the case. So isn't the point to capture as much good data as possible. Larger pixels on the sensor may make for fewer numbers (less data), but for better image quality.

You also say to send as much data as possible to the output device. What is the point of sending an output device more data than it can use. If you know beforehand that the only place you will ever show your pictures is on the web at resolutions about 400x600, wouldn't that have alot of implications for your work? and allow you to cut alot of corners?

Why is it so important to work in layers and keep the original data clean on the bottom layer? As long as you save a backup copy of your original, then all of your original data is saved. When you go to a print, everything gets flattened anyway. So what is the problem with intermediate flattening (done judiciously), if it neither destroys your backup copy nor effects your final print? Is there something I don't understand about the value of layers?

Duffy

arodney

Jul-05-2007, 11:41 AM

You say to capture as much data as possible. One might conclude from this that more megapixels is always better, because more pixels means more data. It's pretty clear that that is not the case.

More doesn't necessarily mean better! I'd take a 13mp capture off a medium format back with say Hasselblad lens than a 16mp off a DSLR. I'd take a much smaller file off a true scanning back (Betterlight) than a single shot device (assuming nothing is moving). But once you pick the capture device, keep and use all the data it provides. Reducing its gamut or bit depth is what I'm suggesting you avoid.

You also say to send as much data as possible to the output device. What is the point of sending an output device more data than it can use. If you know beforehand that the only place you will ever show your pictures is on the web at resolutions about 400x600, wouldn't that have alot of implications for your work? and allow you to cut alot of corners?

One is speed and the other is ease of use. At the Epson Print Academy, where we speak, we try to dispel the idea of downsizing your files for print. IF the data you wish to use falls within a range of 180-460ppi, just send that to the driver. You save time, you're not making multiple versions and you're sending all the data in the document to the print driver. Once you setup the document to be say 20x30, it will (if you have enough data which you should look at) produce optimal quality as long as you don't go over 460 or less than 180.

Some 3rd party print drivers, for example ImagePrint can use the full 16-bit data path out to the printer. Photoshop will sample the 16-bit document on the fly to 8-bit using Print with Preview (Print in CS3).

Why is it so important to work in layers and keep the original data clean on the bottom layer?

With the exception of cloning say dust, keeping the underlying data intact allows you more flexibility in editing. So the only edits I actually stamp on the bkgnd layer are clones that I know I want forever. Otherwise, all work is done on adjustment or other layers.

As long as you save a backup copy of your original, then all of your original data is saved.

I prefer to keep a single master that has all the edits I need intact. It just makes file management easier, I always have the edits I can turn on or off based on what I wish to do with the data (where the data will be output).

When you go to a print, everything gets flattened anyway. So what is the problem with intermediate flattening (done judiciously), if it neither destroys your backup copy nor effects your final print? Is there something I don't understand about the value of layers?
Duffy

Correct, when you print, all the visible layers are in essence flattened. So much for non destructive editing <g>. And I will flatten some layers if I'm fully convinced that I want to stamp that data into some underlying data (but again, I keep the bkgnd layer alone).

From a practical standpoint, using one document with multiple layers or a dozen different document with specific edits provides the same results but the difference is having all the various edits in one place, with the ability to toggle them on and off based on your current needs and a much easier file management route. Also, depending on the edits and the blend modes, you'll get differing effects with multiple layers as opposed to multiple documents. The key (one of Mac's best teaching practices) is very through layer naming conventions. Everything must have a name. He recommends using the Annotation's as well to provide non printing instructions on what was done and why. If you have to revisit a file you worked on a year earlier, this can really be useful. Also useful having the various layers on one document when working with clients who want to see variations or want edits changed (not that a client would ever change their mind about what they want you to do ....).

Layers can, depending on their type take up less storage space than having the edits stamped onto the pixels. A layer with lots of transparency will take up less space than one with lots of pixel data. Adjustment layers take up very little space, they are the closest we have in Photoshop to true metadata editing instructions.

LiquidAir

Jul-05-2007, 12:21 PM

Another example. For years, people have been told to convert a file to LAB to sharpen the L channel. Well that takes time and causes more data loss than just using USM and the Fade Luminosity option plus you also have the opacity slider. Are the mathematically identical? No, one tosses more data in the process but the end result is avoiding color fringing from the sharpening thanks to using the Luminosity blend mode. Better, Faster, Cheaper: pick any two.

I am still a bit of a beginner at this, but after reading Dan's "Photshop LAB Color" book, I came to the conclusion that the real point behind going to LAB is to have independant control over contrast and saturation. RGB curves are the commonly recommended way for beginners to increase saturation, but the standard S curve has the by product of generally (but not universally) increasing saturation and they also end up with a bevy of subtle hue shifts. My impression is that the look of RGB curves is popular not because it is realistic, but rather because it mimics the behavior of high contrast slide films like Velvia.

In the digital world, I don't always want a film look, so I tend to lean in the direction of separating out my contrast, saturation and hue decisions. In my normal workflow, I tend to sort out my hue issses first; for typical photographs that is done with a combination of white balancing and calibration in Lightroom/ACR. Once I have the hues where I want them I go to Photoshop to increase contrast and saturation. I generally avoid doing major contrast adjustment in ACR or Lightroom because of color artifacts introduced by the RGB curves. Also, I prefer to settle on my final luminance curves after I have done any local contrast enhancement. A note here: sharpening, local contrast enhancement (HIROLAM sharpening in Dan's language), and Luminance curves are all contrast moves in my book.

The question I am left with is should I handle my contrast and saturation moves in RGB or LAB?

In RGB I create a Luminance Blend layer for the contrast moves and a Hue/Saturation layer for the saturation moves.

In LAB, I use a Curves layer for my saturation and luminance curves. LCE and sharpening happen in the L channel of the of the background.

If I am not doing anything fancy, I can get essentially the same result either way. However, I am not sold that I lose less of the original data by staying in RGB because there is an implicit colorspace conversion to HSL inside the Hue/Saturation layer. I am also not convinced that staying in RGB is faster because adding a luminance layer for sharpening increases my file size and memory use (does this get better in CS3? I am still using CS2).

In practice my default answer has been that if I am going to adjust saturation I prefer LAB over RGB. However, if all I am doing is increasing contrast (usually when I am sharpening at my output resolution), I prefer to avoid the color space conversion and use a Luminance layer in RGB. That said, I have a set of color space specific tricks I use for particuar image problems that will either force me to stay in RGB or force me to convert to LAB. Also, if I have a real tough nut image that I am going to fiddle with a lot, I tend to stick to RGB so I can leave all the layers in my ProPhotoRGB master rather than flattening them out when I do the colorspace conversion.

In the end, it seems like the sharpen in the L channel vs. sharpen in a luminance blend layer debate seems to me making a mountain out of a mole hill. I am happy to do either and I make my choice primarly based on what else I am doing to an image.

arodney

Jul-05-2007, 12:57 PM

I generally avoid doing major contrast adjustment in ACR or Lightroom because of color artifacts introduced by the RGB curves.

Artifacts? Can you elaborate?

LiquidAir

Jul-05-2007, 01:44 PM

Artifacts? Can you elaborate?

If you take an RGB triad and apply the same non-linear curve to the R channel, G channel and B channel, unless R=G=B, each color will fall in a different part of the curve. Even when all three curves are identical, the result will curves will be to shift the hue of some (but not all) colors. I'll see if I can put together a simple PSD file which demonstrates this effect.

arodney

Jul-05-2007, 02:00 PM

If you take an RGB triad and apply the same non-linear curve to the R channel, G channel and B channel, unless R=G=B, each color will fall in a different part of the curve. Even when all three curves are identical, the result will curves will be to shift the hue of some (but not all) colors. I'll see if I can put together a simple PSD file which demonstrates this effect.

OK I thought that was what you might be refrerring to ala Dan but the term artifact threw me.

You realize that this behavior is done by design and in fact takes more code and work on the part of the Adobe engineers to do?

This is a quote from Mark Hamburg on ACR/LR curves:

Question. Does ACR/LR use a RGB "master curve" (composite curve) when applying brightness/contrast or the curves? Or is it working on luminance data?

Answer: Neither actually. Lightroom and Camera Raw preserve hue but adjust saturation to match with contrast changes because having saturation and contrast get out of sync tends to look rather odd.

Duffy Pratt

Jul-05-2007, 02:09 PM

Andrew:

Thanks for your patience on this. I have found this thread to be quite illuminating.

If I had an ideal set-up, I would probably adopt many more of your recommendations than I now follow. I am working on a four year old laptop with an OK 17" screen and 2 gigs of memory. I'm using PS CS1 for editing.

With this setup, 16 bit editing is basically out of the question. I would tear my hair out waiting for re-draws of the images. For similar reasons, opening a bunch of files to do skin tone comparisons is also out of the question. My machine cludges along as it is.

Similarly, calibration is only useful to some degree for me. Change the angle of the laptop screen a degree or two, or simply slouch a bit, and alot of the benefit of calibration plunges down the drain. This doesn't even get into the effect that changing light has on a laptop screen.

Someday, I may have the money (and convince my wife to spend it) so that I can have basically unlimited performance and storage. Today isn't that day, so I try to live with the best compromises I can afford.

From what you wrote, one of the main advantages of working with and preserving layers is for when you come back to a file after a long period of time. My attitude about that is that I am still learning so much that the main thing I would learn going back to a file in a year is how stupid I was a year ago. So I'm content to start from scratch.

Think about this. Suppose you had a RAW file that you processed with some early version of ACR and then polished up in PS a couple of years ago. You might now want to go back and do some stuff with the file, but it might be better and quicker just to go back to the RAW, process it with the new ACR or Lightroom, and finish it up with whatever your new processes and knowledge have taught you in the meantime. Since I'm still very much on the steep part of the learning curve, it seems pretty obvious to me that I could do a better job faster on just about any picture I took a year or a year and a half ago.

Thus, preserving my work simply isn't a priority for me. In principle, I'd like to know how, and I intend to learn how to do this easily at some point. But right now, everything I do is just a bunch of compromises.

Duffy

arodney

Jul-05-2007, 02:20 PM

With this setup, 16 bit editing is basically out of the question. I would tear my hair out waiting for re-draws of the images.

You youngsters <g>. I recall, back in 1990, Photoshop 1.0.7 on a Mac Iici, 16 megs of ram, I had to rotate a 25mb image I shot 1 ½ degrees because the 4x5 wasn't perfectly level. It took 22 minutes to process! Fun.

I actually started my conversations with Adobe (to later become an alpha and beta tester) by recommending Beep when done. Just took too much effort to keep looking up from reading material to see if the progress dialog was dismissed.

Anyway, I understand your point. But trust me, whatever you're doing, it ain't that slow!

Similarly, calibration is only useful to some degree for me. Change the angle of the laptop screen a degree or two, or simply slouch a bit, and alot of the benefit of calibration plunges down the drain. This doesn't even get into the effect that changing light has on a laptop screen.

Don't have that problem with my Sony Artisan's. Yup, I'm not a fan of LCD's for color critical work. They are getting better. Once the Fluorescent lights are gone, they will be a lot better. Actually, viewing angles are getting pretty good these days.

Think about this. Suppose you had a RAW file that you processed with some early version of ACR and then polished up in PS a couple of years ago. You might now want to go back and do some stuff with the file, but it might be better and quicker just to go back to the RAW, process it with the new ACR or Lightroom, and finish it up with whatever your new processes and knowledge have taught you in the meantime.

The beauty of raw is it's just a data source. As the converters get better, its actually useful to revisit the rendering from square one because you can produce vastly superior results. What's really cool about Lightroom is the edit list that remains intact after you quit the application. Or the ability to build variations, multiple rendering instructions.

LiquidAir

Jul-05-2007, 02:29 PM

OK I thought that was what you might be refrerring to ala Dan but the term artifact threw me.

You realize that this behavior is done by design and in fact takes more code and work on the part of the Adobe engineers to do?

This is a quote from Mark Hamburg on ACR/LR curves:

Question. Does ACR/LR use a RGB "master curve" (composite curve) when applying brightness/contrast or the curves? Or is it working on luminance data?

Answer: Neither actually. Lightroom and Camera Raw preserve hue but adjust saturation to match with contrast changes because having saturation and contrast get out of sync tends to look rather odd.

Oh interesting. I wasn't aware that the ACR/Lightroom curves worked that way. I know I have ended up with some wacky colors and oversaturated images when I have started with low contrast orginals. However, it is possible that the black point and exposure controls were at fault rather than the curves. I love the idea of a Lightroom only workflow, and I certainly go that route for family snap shots and the like because of the efficiency. However when I really want to make an image look its best I have had a hard time getting there without Photoshop. With the addition of the Clarity control and the improved sharpening, there does seem to be the potential to go that route with more images.

As for increasing contrast without increasing saturation, he is right. It often does look strange. However, I don't always agree with Lightroom on how much to increase the saturation for a particular curve and image. The saturation and vibrance sliders are there to help with this problem but so far I have not found the results to be completely satisfying. I'll have to toy around in Lightroom to see if I can figure out how to duplicate the net effect of my standard LAB workflow.

patch29

Jul-05-2007, 02:30 PM

Don't have that problem with my Sony Artisan's. Yup, I'm not a fan of LCD's for color critical work. They are getting better. Once the Fluorescent lights are gone, they will be a lot better. Actually, viewing angles are getting pretty good these days.

Have you seen the new Lacie 526 (http://www.lacie.com/us/products/product.htm?pid=10896), not sure if it is even in production? I am wondering how it compares to the Artisan.

LiquidAir

Jul-05-2007, 02:36 PM

For similar reasons, opening a bunch of files to do skin tone comparisons is also out of the question. My machine cludges along as it is.

One thing I have considered doing is creating a small file with a bunch of color patches of reasonable skin tones to use as a reference. Something akin to that might put a smaller load on your machine than opening a full image.

LiquidAir

Jul-05-2007, 02:41 PM

Don't have that problem with my Sony Artisan's. Yup, I'm not a fan of LCD's for color critical work. They are getting better. Once the Fluorescent lights are gone, they will be a lot better.

Indeed. I use a cheap $200 ViewSonic CRT and for critical work I prefer it to any LCD I am willing to pay for. I have found that if I am preparing an image for the web that I do need to view it on my LCD at work so I know what most people are (or more to the point, aren't) seeing.

arodney

Jul-05-2007, 02:58 PM

Oh interesting. I wasn't aware that the ACR/Lightroom curves worked that way. I know I have ended up with some wacky colors and oversaturated images when I have started with low contrast orginals. However, it is possible that the black point and exposure controls were at fault rather than the curves.

That's why generally its best to work with the tools in the order presented (top down, left to right). There's a fixed processing order by design. That's one reason you see two histograms that look different. The one in Curves is based on the data after using the basic controls. You can of course work out of order but you might end up chasing your tail.

I love the idea of a Lightroom only workflow, and I certainly go that route for family snap shots and the like because of the efficiency. However when I really want to make an image look its best I have had a hard time getting there without Photoshop.

Its important when talking about raw processing to look at the vast differences in the two tools and the data being affected. I do all the heavy lifting (tone and color) in LR. its faster, its operating on a very different kind of data than baked, colored pixels in Photoshop. Its all metadata instruction being applied to a data source. There are operations that simply can't be duplicated in Photoshop on gamma corrected images (like WB, highlight recover etc).

There's is still areas that need addressing such that I'd spend even less time in Photoshop such as soft proofing and output sharpening (capture sharpening in 1.1/4.1 is very nice). I still need to move into Photoshop to do output sharpening and soft proofing at the very least and of course precise pixel editing. The healing brush is awesome when you need to remove a dust spot on 100 images but precise cloning? Nope, you need Photoshop which is a true pixel editor.

Look I have a pretty good road map for what's coming in LR (and no, I'm not talking <g>). We'll all be using Photoshop but a lot of work can and I would submit should be done from raw data in LR, ACR or another processor (if you're on the Mac, Raw Developer is also a very good package although it doesn't handle a fraction of the other functionally of LR and the other modules). Printing out of Photoshop is a drag, a great experience in LR.

With the addition of the Clarity control and the improved sharpening, there does seem to be the potential to go that route with more images.

Indeed. Clarity was something I had to do in Photoshop on a routine basis and don't anymore. That's originally a wonderful technique that came from Mac Holbert at Nash editions for doing Midtone contrast tweaking. You can do it in Photoshop easily (I have an action that does it) but now I just use Clarity in LR.

arodney

Jul-05-2007, 02:58 PM

Have you seen the new Lacie 526 (http://www.lacie.com/us/products/product.htm?pid=10896), not sure if it is even in production? I am wondering how it compares to the Artisan.

One is on it's way for review. It's actually an NEC product that LaCie OEM's.

patch29

Jul-05-2007, 03:44 PM

One is on it's way for review. It's actually an NEC product that LaCie OEM's.

Will NEC sell it also or only via LaCie?

Hope you receive it soon, looking to hear your opinion of it.

arodney

Jul-05-2007, 04:09 PM

Will NEC sell it also or only via LaCie?

I expect NEC will sell it too. I'll ask.

rutt

Jul-05-2007, 04:35 PM

Because for skin tones CMYK and LAB both provide an understandable relationship that can provide an important guideline as to whether you're on target or not. I've never found an RGB equivalent. If you can provide me with one, I'd be ecstatic. But so far, only CMYK and LAB can do this. I know that Y should be a few point greater than M, and that C should be a fraction of either of them. Or, in LAB, I know that B should be more than A. They're not hard and fast rules, but it's a great aid in making sure that your skin tones are correct. And this cannot be replicated in RGB.

In RGB, you want G >= B with both a fraction of R. It's really just the inverse of the CMYK guideline you are used to. If G >= B, then M <= Y and A <= B in LAB. At this very gross level of approximation (and that's really all this is) CMYK is RGB. That's very different from the fine distinctions Andrew wants to make. These guideline are just to get a rough idea whether things can be improved.

arodney

Jul-05-2007, 05:23 PM

Brand new PDF just appeared on the Adobe Site today by Dr. Karl Lang (he designed the Radius Pressview then the Sony Artisan reference display). He's a very good tech editor too.

http://wwwimages.adobe.com/www.adobe.com/products/photoshop/family/prophotographer/pdfs/pscs3_renderprint.pdf

Read it, then consider what I've suggested about scene versus output referred, accurate color, and so forth.

BinaryFx

Jul-07-2007, 08:19 PM

In RGB, you want G >= B with both a fraction of R. It's really just the inverse of the CMYK guideline you are used to. If G >= B, then M <= Y and A <= B in LAB. At this very gross level of approximation (and that's really all this is) CMYK is RGB. That's very different from the fine distinctions Andrew wants to make. These guideline are just to get a rough idea whether things can be improved.

Thanks John, I have briefly covered this in another thread here, but I may as well take the time to "flesh out" the point again in this topic (sorry about the pun, it was intended).

I entered digital imaging before Photoshop was king (originally as a compositor and then into general prepress), way back in the time of proprietary prepress colour systems and drum scanning, before the "desktop publishing" revolution. Since I "grew up" in the subractive colour world of ink on paper, I am very comfortable evaluating colour in SWOP TR001 or similar CMY(K) - but like DavidTO and many others, find doing the same thing in the additive RGB mode harder. Perhpas for different reasons, David may not have a prepress background. The subtractive mixing of colour is understood by children when painting, with a little experience. Often photographers who view the world in light find RGB colour mixing and evaluation more intuitive.

As Rutt correctly points out, in "theory" RGB is the inverse of CMY, so it should be no big deal to think "opposite". As printing inks are not pure, they are not simply the exact inverse of RGB values in a synthetic RGB working space in Photoshop...but we are not talking of such absolutes here, just a general ratio. For the task at hand, the general rule still applies with a little variation and adjustment, depending on the RGB working space at hand (just as the CMYK numbers depend on the 4C print process they are targeted to).

Nobody is saying that there is a magical and correct CMYK recipe for "correct" skin, or other "memory colours" such as blue sky or green foliage. What has been found over the decades in print production is that there is a ratio of cyan to magenta and yellow that produces a pleasing result on press. Most often the CMY ratio is presumed to be for a web press or other common offset print condition with a similar gray balance. The reason that such numerical evaluation and adjustment was necessary was due to the technology of the time. Drum scanning used to be performed with no preview on a monitor of the scanned image, but they could sample colour readings from areas of the image to evaluate what was taking place with the scan and the on the fly conversion to the chosen CMYK settings and to make adjustments if needed. These adjustments or "corrections" were not simply chosen at random, a drum scanner operator used to serve a four year apprenticeship learning the craft.

Today with RGB originals and Photoshop, one does not have to evaluate colour in CMYK mode. As has been noted in this thread, there are other colour models that may serve the purpose better. Andrew mentioned his preference for LCH that was made popular in old LinoColor scanning software - while John, David and others have mentioned that LAB mode evaluation in Photoshop via info palette is a similar and viable option that they employ. HSB mode could also be used for skin, but it should not be used for evaluation of neutral shadows.

Obviously, I find the info palette and colour sampler tool in Photoshop to be a critical part of my workflow. Another important palette is the color palette. One can sample an image colour and view the ratio of the various channels in different colour modes via the position of the sliders. The sliders indicate a pleasing ratio for a given colour based on their position or the "shape" that they make.

The basic evaluation method that the prepress industry came up with decades ago is to sample a representative area and find the magenta value. This establishes the basic level in the skin. The yellow value is usually at least equal to and slightly higher than the magenta value, perhaps 10-30%, one now has a hue change from light pink to light red. The cyan value is the critical one and seems to be missed when visual evaluation only is performed, even if on a calibrated/profiled/colour managed monitor and software etc. The basic guideline is that the cyan should be anywhere from 1/8 to 1/3 the magenta value (higher cyan with higher magenta and yellow for a good strong tan, faces and children will vary this guideline). The cyan kills the red and gives the skin hue a realistic appearance and depth. As has been noted by many, skin being too red in print (press, inkjet) is more often due to a poor red/cyan channel than the green/magenta and blue/yellow being the main problem, although they may need tuning as well.

To illustrate this point, I have attached an animated GIF image to this post. The old PDI test image has been used to provide two common samples of skin in "normal" lighting. This image has not been "corrected" or "enhanced". This is the original colour. The posted image is sRGB, but the original colour values illustrated are Adobe RGB and SWOP v2 CMYK (TR001), in addition to LAB. In all cases, the same basic ratio can be found, as indicated in the animation. With such a simple rule/ratio to follow, one can be confident that the reproduction of skin will be pleasing, where as in the past one may not have been sure of this.

As many people have stated - using colour managed monitor and the info palette is the best approach. The info palette can be used for evaluation of memory colours and not just endpoints/neutrals, although some only advise the later and not memory colours.

One can read about memory colours in this short extract/review:

http://www.panix.com/%7Erbean/color/color4.txt

Sincerely,

Stephen Marsh.
http://members.ozemail.com.au/~binaryfx/

DavidTO

Jul-07-2007, 08:43 PM

BinaryFx

Jul-07-2007, 08:46 PM

These are the two skin samples in question. The old CMY formula traditionally used by prepress is verified by modern capture and colour conversion. As the previous animation indicates, color palette evaluation in RGB, CMYK or LAB mode will result in similar indicators of pleasing skin tone.

All colour spaces are one, as somebody once said.

Regards,

Stephen Marsh.
http://members.ozemail.com.au/~binaryfx/

BinaryFx

Jul-07-2007, 09:32 PM

jfriend

Jul-07-2007, 11:10 PM

As many people have stated - using colour managed monitor and the info palette is the best approach. The info palette can be used for evaluation of memory colours and not just endpoints/neutrals, although some only advise the later and not memory colours.

Well said Stephen. Thanks for taking the time to write this.

Tim Lookingbill

Jul-08-2007, 12:29 PM

arodney

Jul-08-2007, 12:32 PM

Yeah,

And that PDI fleshtone target can take on a tinge of orangey to pinkish yellow then to rust, to maroonish brown just by taking a bathroom break. The blue background doesn't make it any easier as well. Sheer torture.

I hate that document and wish people would instead use better examples of possible color scenes. Bill Atkinson has some excellent targets on his site.

Duffy Pratt

Jul-08-2007, 02:34 PM

In this iTunes/QuickTime podcast video for Adobe Photoshop Lightroom, there is a visual method of adjusting colour - which I presume is similar to what Andrew Rodney suggests, rather than more extensive use of the info palette that John and others have gained appreciation for from books from Dan Margulis. Granted, this example of editing is more subjective than targeted, which is the point I guess!

http://av.adobe.com/russellbrown/20070614_Lightroom_Tutorial_Podcast.mp4

I watched that video and was amused by the number of times he used the word "correction," sometimes correcting himself about his own "misuse" of the word. One thing that he doesn't seem to understand is that the verb "correct" can mean to make something more accurate, or sometimes it simply means to adjust something. Thats just a small semantic point.

The idea underlying it bothers me some. Some people seem to think that just because a process doesn't lend itself to accuracy that can be measured by a machine, then it must be "totally subjective." I think this is a mistake. There are lots and lots of areas of human activity that are neither scientifically measurable nor totally subjective. To a large extent, color correction is one of these areas. There may be no single right way to correct a photo, but there are many, many wrong ways to do it. Right and wrong here are matters for agreement, not for measurement.

Recently, we also discovered that reading an election ballot was one of these areas that lies in the middle. No machine could say whether a hanging chad was a vote, but that did not make the process of reviewing the ballots "totally subjective" either. My guess is that there are many, many things we do every day that fall in this middle area, and our sometimes sloppy words actually work well in these sloppy domains.

Duffy

LiquidAir

Jul-08-2007, 04:13 PM

I hate that document and wish people would instead use better examples of possible color scenes. Bill Atkinson has some excellent targets on his site.

I went hunting on his site for those and coudn't find them. Would you mind posting a link?

BinaryFx

Jul-08-2007, 04:14 PM

I hate that document and wish people would instead use better examples of possible color scenes. Bill Atkinson has some excellent targets on his site.

One common memory colour that is often critical is pleasing reproduction of skin. I doubt that there will be much argument from the folk here at DG on this point.

The Atkinson composite image test does not include any new skintones (the LAB image, right?) - the only skin featured is a reduced version of the PDI chart that is being maligned!

So, It would appear that the theory is not being dismissed, just the reference image? OK, then...

So, let's try a different reference image for skin tone, the replacement image for the old PhotoDisc, now the Getty Images Test Image:

http://creative.gettyimages.com/source/services/ColorResources.aspx
http://creative.gettyimages.com/en-us/marketing/services/Getty_Images_Test_Image.jpg
http://creative.gettyimages.com/en-us/marketing/services/Getty_Images_Test_Image.tif

The Caucasian lady to the left, an average skin reading in CMYK (Adobe SWOP v2 Web Coated TR001) and RGB (Adobe RGB 1998) is:

16c 47m 51y 0k
191r 141g 110b
65L +23a +28b

Once again, the old prepress CMY ratio and the Photoshop Color palette slider positions in RGB and LAB show a helpful relationship as a guide to pleasing colour. The RGB skin is not out of gamut for SWOP v2 CMYK. Again the image was not edited by me to conform to the legacy target values suggested by prepress tradition, the original colour was captured/presented this way by the test target creator as an "accurate" rendition of the photographed scene. That human observers and modern capture/colour conversion agrees with the old prepress general ratio is not surprising to me.

It really puzzles me why some are so resistant to admit the benefit of taking colorimetric readings inside Photoshop using the info palette and various colour reading modes, for all areas of the image and not just endpoints and known/presumed neutrals. These same people often advise similar measurement based methods (using hardware & software not built into Photoshop) for calibrating and profiling monitors and inkjet printers - but seem to reject similar methods of evaluating images and image edits inside Photoshop using the built in tools provided.

To each, their own - I guess!

Regards,

Stephen Marsh.
http://members.ozemail.com.au/~binaryfx/

Tim Lookingbill

Jul-08-2007, 07:20 PM

The one thing that can throw a monkey wrench into using the numbers for fleshtones is if the subject has that pinky peach foundation makeup. It can imbue an overly vibrant appearance due to its spectral reflectance qualities causing cyan and yellow numbers to get thrown off.

I have never edited any image for output to a commercial press, but I can see how difficult it must be. I flipped through one of Scott Kelby's books illustrating a skintone edit tip in the bookstore one day. It was the one of a close-up on a woman's face wearing sunglasses and noticed the before picture looked better than the corrected shot which made her look jaundice. Maybe it was press drift. Not sure. The tutorial did show the CMYK readouts and I couldn't tell if the amount of yellow was too much or not.

There is one color target where I could actually confirm CMYK readouts as being predictable as they should appear on press and that was viewing a print of the untagged Ole No Moire color target found on PS install CD's printed from Copy Craft's sheetfed Komori waterless press at 300lpi.

This press uses a closed loop color check system using a constantly scanning spectrophotometer that automatically adjusts for press drift, so the CMYK dot percentage sizes in the PS readouts reads exactly that on the print as viewed under a magnifying glass. But the print still showed overall gain in the cyan channel in neutrals, but the fleshtones were spot on.

Also this untagged CMYK target looks way too light when assigning PS's standard coated SWOP v2 so I assigned the sheetfed v2 and the image looked much more closer to the Komori print. See attached scan of the print next to the assigned sheetfed profile on the right.

The problem I've always had viewing dot sizes off press runs is you can't see the yellow because it's too light. Doh!

BinaryFx

Jul-08-2007, 07:27 PM

The one thing that can throw a monkey wrench into using the numbers for fleshtones is if the subject has that pinky peach foundation makeup.

Agreed Tim, as mentioned earlier, children and faces change things a lot. Ideally one can sample many areas and take it all with a grain of salt, remembering that these are just guidelines or they can become more specific and targeted to output if this is a "correction" to a "known" problem rather than just a subjective general edit in an intermediate working space.

I just checked the famous "musicians" scene of the Caucasian, Asian and Negro women with their instruments and ethnic dress, that was originally presented as untagged CMYK. I averaged 10 common press spaces of this image into an ECI-RGB file and an average non facial area of the Caucasian lady on the left is:

18c 36m 49y 0k (SWOP v2)
197r 164g 133b (Adobe RGB)
72L 14A 24B

Again, a similar pleasing ratio is reflected in the color palette via the position of the CMYK/RGB/LAB sliders, as shown in the animation on page 8 of this thread. Note the difference in colour and tone from the Getty image, both ladies are very different and so is the lighting - but both are acceptable (one could argue that the Getty woman is too dark and magenta or the musician too yellow and or not magenta enough etc, this is the subjective nature of such evaluations).

Stephen Marsh.
http://members.ozemail.com.au/~binaryfx