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Bodley
May-04-2005, 04:49 AM
As discussed in the "Price increase" thread, the 12-JPEG is considerably larger than the 10-JPEG. 10-JPEG would increase upload and download (when this service is available) speeds since it is smaller. Also, would help keep cost down for Smugmug which would trickle back to the customers. And according to the few comments there is no perceptible visual loss in photo quality in 10-JPEG.

I've also read to always save in 12-JPEG. And that each time one opens a JPEG and then saves it the file is degraded therefore less compression is better - 12-JPEG.

My "uneducated" questions are: What happens to the data? Is it all still there just compressed? Is part of it discarded? Is 10-JPEG just as good for larger print sizes?

Thanks,
Greg

jfriend
May-04-2005, 07:40 AM
As discussed in the "Price increase" thread, the 12-JPEG is considerably larger than the 10-JPEG. 10-JPEG would increase upload and download (when this service is available) speeds since it is smaller. Also, would help keep cost down for Smugmug which would trickle back to the customers. And according to the few comments there is no perceptible visual loss in photo quality in 10-JPEG.

I've also read to always save in 12-JPEG. And that each time one opens a JPEG and then saves it the file is degraded therefore less compression is better - 12-JPEG.

My "uneducated" questions are: What happens to the data? Is it all still there just compressed? Is part of it discarded? Is 10-JPEG just as good for larger print sizes?

Thanks,
Greg
If ALL you are going to do with an image is print it or view it and you NEVER want to edit it again, then a 10-JPEG is all you ever need. You will not be able to see an advantage with 12-JPEG and the file will just be larger.

If you may be editing the JPEG image again or if the recipient (in a digital download) may be editing it again, then in some cases you will achieve higher quality results by saving the intermediate JPEGs at quality level 12.

In general, if you are going to edit, save, close, open, edit, save, close an image, then you should NOT use JPEG as the storage format. You should use a non-lossy format for your intermediate saves such as TIFF, PSD, PNG or JPEG2000. JPEG is a lossy compression algorithm. Each time the image bits are changed and it is then recompressed for JPEG, the image quality is slightly degraded by the lossy JPEG compression. The slight degradation is greater at quality level 10 than quality level 12. The original point expressed here on this forum is that if you are saving the image only once then quality level 10 is indistinguisable from quality level 12 when viewing on screen or printing. But, if you repeat that process and edit/save several times at quality level 10, the cumulative compression losses will degrade the image and can be noticable.

You ask what happens to the data when a 10-JPEG file gets smaller? In the process of doing this extra compression, the compression algorithm fails to capture certain types of very small detail. Skipping the inclusion of this detail is what results in a smaller file (less information recorded in the saved file). Some or most of that extra detail that is not captured is likely not visible, but it may become visible if you subsequently edit/change the file again and again save it at the 10-JPEG level. To put things in perspective here, in most cases, we are not talking about big effects in your images at the 10-JPEG level. If you go to level 8 or level 6, the effect starts to get a lot more pronounced.

--John

winnjewett
May-04-2005, 09:54 AM
Does someone know what the corrolation between the 1 to 12 scale and the 100% scale is? Is it linear? Or is it something else?

-Winn

colourbox
May-04-2005, 10:04 AM
The point above is correct. You should be keeping high-quality originals on your computer for editing (preferably in TIFF or PSD format), and only uploading JPEGs that will never be edited again, meaning the compression only needs to be good enough to view or print.

Does someone know what the corrolation between the 1 to 12 scale and the 100% scale is? Is it linear? Or is it something else?

Yeah, would someone answer this please? It was already asked before and I'm just as curious about the answer. Thanks!

mercphoto
May-04-2005, 10:30 AM
Does someone know what the corrolation between the 1 to 12 scale and the 100% scale is? Is it linear? Or is it something else?

What do you mean by the 100% scale?

winnjewett
May-04-2005, 11:35 AM
What do you mean by the 100% scale? In many image editing programs, your options for saving a jpeg go from 1 to 100 instead of 12. If you have photoshop, go to file --> save for web for an example. Bibble works the same way.

-winn

Baldy
May-04-2005, 12:07 PM
Here's a good reference on comparing the scales:

http://www.photo.net/learn/jpeg/#qual

If you save a jpeg file repeatedly at the same compression level, it doesn't create further losses. But if you go up or down on the scale, it does alter the image.

I know I'm a terrible broken record, but forum posts and Photoshop books are stuck on the 3 factors that are almost never an issue: pixels, jpeg compression, and how broad the color space is.

By 1,000,000:1, it's color fidelity, brightness, contrast, sharpness, and pollution from UV and infrared light that matter more than those other three issues.

Thanks,
Baldy

marlof
May-04-2005, 12:10 PM
You're forgetting noise. Lot of discussion on noise too. Don't remember that discussion when it was called grain. :)

mercphoto
May-04-2005, 12:26 PM
I know I'm a terrible broken record, but forum posts and Photoshop books are stuck on the 3 factors that are almost never an issue: pixels, jpeg compression, and how broad the color space is.

By 1,000,000:1, it's color fidelity, brightness, contrast, sharpness, and pollution from UV and infrared light that matter more than those other three issues.

But keep talking. People will eventually listen and understand.

colourbox
May-04-2005, 12:32 PM
You're forgetting noise. Lot of discussion on noise too. Don't remember that discussion when it was called grain. :)

Oh, but I do. From what I remember, it was just as bad. A typical article/post would start out "Beginners tend to be obsessed with grain. But grain must be examined within the overall..."

Mitch
May-04-2005, 12:35 PM
A little off topic, but what ever happened to jpeg2000? If I remember correctly it was going to fix all the problems with .jpg.

Mitch

Baldy
May-04-2005, 01:28 PM
But keep talking. People will eventually listen and understand.Okay :D . Here's a help section work-in-progress about a topic I so wish was talked about more:

http://www.smugmug.com/help/printing/red-skin-tones

Baldy
May-04-2005, 01:41 PM
BTW, back on topic: here's what whcc (a very respected printer) has to say about compression:

Why a level 10 JPEG, donít you lose quality? How can taking my file from 18MB to 1.5MB make a good print?
JPEG compression is a very efficient, lossy image compression algorithm designed specifically for saving photographic
images. It takes advantage of how humans see color versus brightness to only save information needed to reproduce
the image for people to view. Image data is lost during compression, but at high levels of quality you will not see
a difference between a Level 10 JPEG and a TIFF printed to photographic paper. JPEG compression is perfect for
transient files for sending to the lab for printing, but avoid using the compression as a working file type. Also
avoid opening a JPEG, making changes, and resaving it again as a JPEG repeatedly. If your workflow calls for this to
happen, save your files as TIFF or PSD files until they are complete and ready for output, at which time you should save
them as a level 10 JPEG. Any JPEG artifacts you see in your prints come from the JPEG file coming out of your camera, not from saving them as a level 10 for output purposes.

Mitch
May-04-2005, 01:57 PM
Baldy,

I just called my local camera store and asked for a uv/ir blocking filter. After explaining what it was, why I wanted it, and what I was going to use it on. I was told that the problem is white balance. If I bought one of the white balance disks and set custom WB that it would fix the problem. No more red skin.

I really wish you would get your facts straighthttp://dgrin.com/images/smilies/icon10.gif.

I'm willing to give the filter a try. Anyone know who might sell them?


Mitch

wholenewlight
May-04-2005, 02:08 PM
I'm willing to give the filter a try. Anyone know who might sell them?

Here's the b&h link for the "486" uv/ir filter. Hopefully it doesn't do what the example shows . . . or I don't think I want one.

B&H Link (http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=235336&is=REG)

Mitch
May-04-2005, 03:35 PM
Here's the b&h link for the "486" uv/ir filter. Hopefully it doesn't do what the example shows . . . or I don't think I want one.

B&H Link (http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=235336&is=REG)
Ummm you know....maybe I'll let someone else give it a try. Spend $150.00 on a filter to get those results? Besides I'm in Phoenix, everyone is sunburn.

Mitch

winnjewett
May-04-2005, 03:38 PM
Here's the b&h link for the "486" uv/ir filter. Hopefully it doesn't do what the example shows . . . or I don't think I want one.

B&H Link (http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=235336&is=REG)
I've been looking for a filter that turned blue skies gray and green leaves orange. Thanks...and at $100, I'll get one for each lens! Sweeet.

-winn

Matthew Saville
May-04-2005, 03:50 PM
First off, is the original poster actually suggesting that Smugmug should make JPEG 10 the maximum JPG compression they allow for uploaded images, to save server space?
Correct me if I interpreted wrongly but in response, I don't think it's possible (or at least optimal) for an image hosting site to actually screen uploaded images for this. I think that once you save an image, there's no way of going back and figuring out what compression level it was saved at. (unless you open it up in PS and look at some dark, deep properties file?) And even if we were restricted in JPEG quality in our uploads, we'd just upload a higher resolution file in the first place. If you're printing at 300 ppi, I doubt most humans would even be able to tell the difference between JPEG 10 and JPEG 7-8...

One other thought I had was, is the original poster referring to the way Smugmug makes it's thumbnail, S/M/L sized images from the original file? Well I highly doubt that Smugmug is creating images on par with JPEG 10 or JPEG 12 compression. As an example, I've got here an image that is very prone to JPEG artifacts, simply due to elements in the subject and background:

http://matthewsaville.smugmug.com/photos/14771608-S
Here is Smugmug's version, the "S" image size.

http://matthewsaville.smugmug.com/photos/21267246-O.jpg
Here is the original "O" from an image I re-sized myself and saved at JPEG 10

http://matthewsaville.smugmug.com/photos/21267247-O.jpg
And finally here's the original from an image I re-sized myself
and saved at JPEG 5. This looks similar to the Smugmug version.


The JPEG 5 image saves at about 25KB and the JPEG 10 image saves at about 50KB. If you go up to JPEG 12, the filesize hits 100KB. (But the optical difference twixt 10 &12 is only for VERY picky people)


Okay, concerning JPEG etc. etc. in general, here's a bit of my own advice, much of which has already been said:

Always "edit-save-edit-save" in a lossless format, just as religiously as you should be USMing dead last in your editing. When making the final file for printing, most labs don't want a 50-layer PSD, so either flatten your PSD or save it as a TIFF.

I like to always keep even my final prints in TIFF or PSD, just in case I ever find out that my monitor was a little off at the time I saved it and I need to run a slight curves / selective color, a few months after the fact.

If you've got to fit a lot of images on a CD or if you're uploading to the internet, don't hesitate to save your images at JPEG 7-10, depending on the resolution and the importance of the print. If you're uploading 2,000 vacation photos and you know you're only going to ever print 4x6's or 5x7's of maybe a few dozen of these shots, then standard procedure should be to upload an image that is 4x6" @ 200/300 ppi, 200 being if you're only going to ever enlarge to 5x7" and 300 being if you think you'll want an 8x12" some day. At 200/300 ppi, you can confidently save your files at JPEG 8 or 9. If you're uploading a larger, more professional type image that possibly OTHERS will be purchasing, whether a 4x6" of a wedding or a 16x20" of Nevada Falls, just try to upload at the best ppi you can, while keeping your filesizes around 5-6 MB. 4 MB for maybe just an 11x14" print and 7 MB for a 20x30" or 30x40" print. Usually this means 180-250 ppi resolution and 9-11 JPEG compression.

If however you're uploading just an 800 pixel "thumbnail" for internet viewing and you intend to make your prints at a local lab, you MUST up the compression to JPEG 10, 11, or 12 in order to preserve all detail since you're essentially uploading a 72 ppi image. I do this with my 900 pixel wide panoramas that I of course have to print at a local lab...

Anything else?

-Matt-