As threatened here, I have an image to work on in which the elimination of the color cast is crucial to the (ahem), artistic vision of the photographer, such as it is. .

Here's the setup:

Shooting raw with my K20d with 35mm f2.8 macro at the Memorial Art Gallery. No flash, no tripods or monopods allowed. Very variable lighting so I'm shooting high iso and AWB. Quite frankly, I'm struggling to keep up with my 5 year old Egyptologist, who desperately wants to see the mummy & sarcophagus of Pa-debahu-Aset:

So I'm walking/trotting down this corridor, and in all this antiseptic museum white, I see these bursts of green around me: the green of sleeve to the left, the green of a stained glass piece, and a painting on my right.

Here's the vision as I raised camera to eye: antiseptic white setting with small bursts of vivid colors, especially greens, on the left, center, and right of me.

When I say vision I'm not trying to be pretentious-- I know this snap isn't going to win any awards-- I just want to be clear what I'm attempting to convey with this picture.

Here's the original, coverted directly from raw. I do use a custom Adobe color profile, as the canned Adobe profile for my camera is quite bad. Anyway, it's underexposed and has a strong cast to it due to the (tungsten?) lights. It's underexposed probably due to the bright stained glass piece directly in front of me fooling my meter.



Here's I white balanced the image as best I could, fixed exposure, and applied some fairly heavy noise reduction:



The next one is my best attempt at cast removal within raw: using the WB sliders and killing the mixed yellow lighting using the HSL sliders to drag down yellow saturation. Unfortunately, it starts affecting the artwork slightly:



Finally: here's the version that gets closest to my vision, and it'll take me a while to write up how I got to it, will add in when I have more time, but I think better can be done:



So I'd like to see how others approach this, given the parameters and the vision I've provided.

If I did this right, you should be able to click on the image to go to the gallery where the originals should be available for download. I'll have to see about finding a way to get the original raw file available as well.

Mark, this is an interesting situation, and a fairly common one I think today. I was not there so I need some information about the scene. I gather the lighting is a mixture of tungsten and fluorescent, giving the yellow green overall tone? Were the walls or the floor REALLY this white? If so, that makes things much easier, of course. You could have shot a grey

I do find fluorescent lighting a lot more today with the advent of Compact Fluorescent energy saving bulbs ( CFLs ) - they fit canisters, and even look like tungsten bulbs, but are green light, not warm yellow tungsten.

You could have shot a white surface to create a neutral jpg for a later custom white balance like with a WHiBal card, or used and Expo disc, but when just casually wandering along is not usually when we have color balance tools at our disposal. I do like this tool a lot - Shoot a frame of it in Av mode and it gives you a jpg for custom white balance, a frame to use in Adobe Camera Raw to use an eye dropper on for WB, and gives you an exact exposure right out of the blocks because it is a mid grey and your shutter speed in Av mode should put the spike in the histogram dead center. Use that exposure for shooting and you should be golden.

I looked at your jpg that you get by clicking on your image. I think you did a very good job, I found far more noise than your final image displayed when I tried to raise your exposure and correct your color balance.

Originally Posted by pathfinder Mark, this is an interesting situation, and a fairly common one I think today. I was not there so I need some information about the scene. I gather the lighting is a mixture of tungsten and fluorescent, giving the yellow green overall tone? Were the walls or the floor REALLY this white? If so, that makes things much easier, of course. You could have shot a grey I do find fluorescent lighting a lot more today with the advent of Compact Fluorescent energy saving bulbs ( CFLs ) - they fit canisters, and even look like tungsten bulbs, but are green light, not warm yellow tungsten.

It was probably either tungsten or cfs that were very yellow-- as I said, I wasn't really paying as much attention as I should have. The mummy was calling to my child.

But I remember everything being very white (walls, floor, ceiling.), which is why the greens stuck out at me.

And yes, I was not shooting smart when I shot this-- I'd like to think next time I would stop and at least use my ColorChecker passport (didn't own it at the time), but who knows. I did get at least one image I like out of that trip, so it wasn't a complete waste of time to bring the camera.

I play tourist a lot too, especially in museums.

Sometimes I can find a known neutral in the scene to balance off of, and sometimes you just have to wing it.

Originally Posted by pathfinder I looked at your jpg that you get by clicking on your image. I think you did a very good job, I found far more noise than your final image displayed when I tried to raise your exposure and correct your color balance.

Mark,

I started to play around with this image and was a bit confounded by the noise. Maybe it's because I didn't start with the RAW. Did you do anything explicit in your workflow to eliminate the noise in the dark areas?

BTW, a very nice communication of your vision and quite a good realization of it, granted not an award-winning shot.

In thinking about your vision, sterile means not only neutral but pretty bright. You did a pretty good job of getting both of these.

Originally Posted by pathfinder I do like this tool a lot

Maybe this should be a new thread. How is this different from a WhiBal?

Originally Posted by jjbong Mark, I started to play around with this image and was a bit confounded by the noise. Maybe it's because I didn't start with the RAW. Did you do anything explicit in your workflow to eliminate the noise in the dark areas? BTW, a very nice communication of your vision and quite a good realization of it, granted not an award-winning shot. In thinking about your vision, sterile means not only neutral but pretty bright. You did a pretty good job of getting both of these.

I really need to make the raw available somehow. In LR3 I used pretty heavy color noise reduction (70%/50 detail) and moderately strong (~30%) luminance noise. I'm still trying to recreate what I did to get to the final shot-- I didn't document very well what I was doing, story of my life. I don't remember doing anything explicit to shadow areas, however.

Raw is here: http://dl.dropbox.com/u/23168823/gal...26%20noise.PEF

Originally Posted by jjbong Mark, I started to play around with this image and was a bit confounded by the noise. Maybe it's because I didn't start with the RAW. Did you do anything explicit in your workflow to eliminate the noise in the dark areas? BTW, a very nice communication of your vision and quite a good realization of it, granted not an award-winning shot. In thinking about your vision, sterile means not only neutral but pretty bright. You did a pretty good job of getting both of these.

I had exactly the same issue, John, the noise just became very large, and hence I bailed. Since Mark has uploaded the RAW file we can give that a try now.

Originally Posted by jjbong Maybe this should be a new thread. How is this different from a WhiBal?

A WhiBal card is a small card 5 x 7 or even 3 x 5 inches that is included in the image, at the time of shooting, and then used INSIDE Photoshop or ACR to click on with the White Balance tool, to obtain the correct color balance for the image. This can work pretty well.



The BalanceSmarter or the Lastolite color balance reflector, is an 18 % non specular grey disc - anywhere form 12 - 30 inches in diameter. You hold up the reflector in the ambient lighting, and with your camera in Av mode, shoot a full frame of the reflector. This will capture an even neutral grey image that on your camera's RGB histogram will appear as a single spike in the center of the span in each of the R,G,B channels. This frame can then be used to set a custom white balance within the camera to shoot custom white balanced jpgs. It also gives you the exposure, since you set the aperture, and the camera chose a shutter speed to give a single spike in the middle of the histogram. In other words, you use the same aperture and shutter speed ( EV ) that the camera used for shooting the grey card.

I wrote about color balance tools here - http://www.dgrin.com/showthread.php?t=90438


One of the nice things about the Lastolite reflector, or the BalanceSmarter disk is that they have a center cross of white lines for your camera to AF onto, and hence you do not have to remember to turn your AF off and then back on again as you do with white paper or an Expodisk, or a SpectraSnap ( which is another filter like the Expodisk )

All these tools do work, some are just faster and a bit easier. If you like the WhiBal card method, there is even a white bracelet of tungsten dioxide that I included in the discussion about color balance tools linked earlier.

Here is my attempt. Noise was a problem throughout, as you might expect from a shot taken in these circumstances. Anyway, I didn't try to perfect the noise reduction, as that's not the point of this exercise, but I did try to make it not particularly distracting.

In Camera Raw (I'm using Photoshop CS3), I adjusted the exposure (higher) and black (to zero). I also set the white point using an arbitrary point on the white walls.

In PS, to eliminate noise, I used the Noiseware plug-in with defaults. I was left with a lot of yellow noise, so I went into LAB, and blurred the B channel, gaussian, at 15.8 px.

My interpretation of how to realize Mark's vision (sterile, burst of green color) was very light neutrals (e.g. white) except for the colors on the right of the image. So I had to kill the residual yellows in the darker parts of the hallway. I did this also in LAB, using a second layer, and Apply Image to the B channel, using the B channel of the background layer, inverted, 50%, Darken. That killed the casts nicely, giving this:



It has some of the characteristics of Mark's vision, but it's not bright enough or colorful enough.

I used the standard PPW color enhancement curve in the A and B channels, at a pretty high opacity (59%), and I used an L curve to brighten everything to make it more sterile. The final thing was to make the Exit sign less distracting by desaturating it with the Sponge tool. Through all of this, I ignored the blown-out areas in the background, as Mark did, I think correctly.

Sharpen and done.



I think it's somewhat better than Mark's attempt, so we'll see what Mark says. Maybe the green needs to be saturated more and lightened, which is not hard. Noise remains, but it may not be possible to get perfection here.

I like the fact that you managed to keep the green reflections from the stained glass in front. The blue painting on the right I remembered as being more blue, but looking at the gallery's website, looked closer to John's: http://magart.rochester.edu/Obj731?sid=40024&x=659571

On first glance, yours seems somewhat reddish, but I have to think about this.

Marc, I finally went back with your RAW file to create this image..

I satred with the file in LR3, but had to take it out to CS4 where my NoiseWare plug in lives.

I took my white balance from the reflector around the tungsten bulb at the end of the hall ( I assumed it was Tungsten )

Once in Photoshop I used curves to reduce the blues in the upper tones, and the greens as well ( Maybe it was fluorescent after all - not sure )

I like what you and John have done to the hallways, but they are so white they look like a hospital, and the green transparency at the end of the hall looks all burned out. I decided that your original frame might be correct for that central area, so I brought a second unaltered copy of the image into Phtooshop, and airbrushed the green picture and green reflection at the end of the hall back into my editied image for this result.




The full size image is here - http://pathfinder.smugmug.com/Other/...446_dAKNk-O-LB

The close end of the hallway in my image is much bluer, I suspect there was a window off to the left perhaps, and I did not correct that area of the image, and I left it dimmer as well. But I prefer the darker forground with the light and contrast at the end of the hallway where the transparency is displayed... It is one interpretation.

Pathfinder, Interesting that both your and John's images have a distinct magenta -- and in your case, even purple--tint. Definitely like how you brought back the stained glass and the reflection.

Just out of curiousity, what DNG profile did you use in raw under the color calibration tool? As I mentioned before I use a custom dual-illuminant one because the Adobe Standard that shipped with LR3 was very off from my camera, specifically a magenta tinge. (The "Camera Standard" profile is much closer to my custom profile than the Adobe one is.)

Here's another picture of that same hallway during another visit for reference. I feel like an archivist, finding pictures I didn't even know I had.
Looking at the raw, the only thing I did was custom white balance (2500/+8), raised the exposure +.70, and raised the brightness in the highlights.

Marc, The file I received for some reason was a PEF, but my LR called it a jpg, not RAW file, and thus the profile was embedded, and I was offered no choice about the camera profile.??

My goal with this image was to correct the far end of the hallway, which I felt was lit by the artificial lights, which I assumed were tungsten. When I measure the end of the hall I think the walls are pretty neutral. Both your and Johns's images are much brighter in the forground than mine. Mine is actually blue in the upper left corner still, one of the reasons I suspected an outside window up there.

I went through a phase where I tested different profiles ( Canon has at least 6 or 8 different ones )for an image, but for EOS images, now I just use Adobe. It seems to work pretty well for my Canon cameras.

I wasn't certain if the stained glass and reflection would match your remembrance, but am happy it meets with your approval. I kind of thought is was the center of you image originally, and I hoped it had been exposed correctly at the time. Seems like that was an accurate guess.

Your new image of that hallway is probably lit by tungsten without contamination by sky light. I see the stained glass is similar to my rendering too.

Hmm.. not sure if you were only getting the embedded preview jpg? Not sure why it would not let you modify the PEF custom calibration-- K20D has been supported since LR1.4!

I will check the dropbox file again and see if I can see what went wrong.

Edit: looks right, at 17.1 MB. I can try converting to DNG and posting to see if that helps.

The file was a PEF file, but it displays with an embedded profile???

Definitely should not be an embedded profile! I believe that is only for pre-rendered images (jpegs and such.) If I pull it from my dropbox and open it in CS5 I get the usual range of profiles (4.4, Adobe, Camera, Custom). I have converted it to a dng and uploading it.

DNG http://dl.dropbox.com/u/23168823/gallery.dng

Originally Posted by MarkR On first glance, yours seems somewhat reddish, but I have to think about this.

I did a pretty aggressive color enhancement using an AB curve in LAB to enhance the saturation of the greens on the right, and this would have also enhanced the magentas. The fix is to change the curve in this step to be steep in the negative A region and less steep in the positive A region. Alternatively, use a blend-if to reduce the enhancement in magenta areas.

If you like the overall effect, I can re-do with this change. Otherwise, otherwise.