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Author Topic: 10D, JPEGs and Adobe RGB  (Read 4144 times)
Arnaud73
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« on: May 12, 2006, 07:36:04 AM »
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Thanks to digital cameras, I know shoot a lot more than I used to (well, I was shooting a couple of rolls a year).

I still shoot a few subject JPEG only by I start to use RAW more often. My default colorspace is Adobe RGB.

My workflow is pretty simple: I import my photos in folders then browse and auto-rotate all the pictures with ACDSee (lossless operation). I view the pictures with ACDSee viewer, and I edit file with PhotoShop.

I was sometimes disappointed with the colors of some pictures. I was even more disappointed when a friend of mine shoot the same subject with a D70 and gave me the files. Colors were much "punchier", mine looked dull...

I've been investigating a little and it seems that at some point, the colorspace information is lost and files are interpreted as sRGB... It does not appear for all pictures but many are affected.

As far as I have investigated, it seems that there are two ways to specify the colorspace for a JPEG file :
- as an image attribute (included profile).
- as an EXIF information (Primary Chromacities)

When the EOS 10D saves a file, it only sets the Primary Chromacities. I see two problems with this method :
- ACDSee and many other tools (Windows) don't use this EXIF property correctly.
- ACDSee was buggy at some point and EXIF data have been modified : event PS did not recognize some pictures as Adobe RGB.

I'm a little confused with all that. How do you guys work with Adobe RGB files ? Have you encountered any similar problem ?

By the way, I'm looking for a simple tool to set colorspace of a bunch of files without having to uncompress-recompress the JPEG data. Does anyone know any utility like this ? I just would like to include a profile within all my JPEGs so that ACDSee interprets them correctly.
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Dennis
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« Reply #1 on: May 14, 2006, 03:26:09 PM »
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Forget ACDSee and use Photoshop Bridge instead. You will get "better" colors, if you set  your camera to sRGB. If you have a good reason to use AdobeRGB, than create a Photoshop action, were you assign the AdobeRGB profile to the camera-JPEG's. If you go Raw - what's recommended, if you have needs for Adobe RGB - you can choose AdobeRGB in the ACR dialog for the output file.

Dennis.
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Best Regards

Dennis.
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« Reply #2 on: May 14, 2006, 03:58:36 PM »
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Is ACDC color managed? If so, what are the color management settings you specify in it?
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Arnaud73
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« Reply #3 on: May 15, 2006, 08:01:54 AM »
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Is ACDC color managed? If so, what are the color management settings you specify in it?
[a href=\"index.php?act=findpost&pid=65452\"][{POST_SNAPBACK}][/a]

ACDSee Pro is color managed. ACDSee is also color managed if you have the pro photo plugin.

I use ACDSee with this plugin. It manages Adobe RGB files OK as long as they embed the right ICC profile. If not, they are handled as sRGB files.

I tested that with one photo which I just opened and saved in PS. After "save", an ICC profile was embedded, so ACDSee displayed it correctly.
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Arnaud73
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« Reply #4 on: May 15, 2006, 08:05:42 AM »
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Forget ACDSee and use Photoshop Bridge instead. You will get "better" colors, if you set  your camera to sRGB. If you have a good reason to use AdobeRGB, than create a Photoshop action, were you assign the AdobeRGB profile to the camera-JPEG's. If you go Raw - what's recommended, if you have needs for Adobe RGB - you can choose AdobeRGB in the ACR dialog for the output file.

Dennis.
[a href=\"index.php?act=findpost&pid=65451\"][{POST_SNAPBACK}][/a]


Thanks for your advice.

In fact I prefer Adobe RGB since I print some of my pictures.

I also developped a few PS macros to convert profiles, mainly to export my pictures to my web gallery.

However, I don't want to open save my hundred of pictures in PS and save them so that an ICC profile is embedded : PS will uncompress and recompress the JPEG image, so there's going to be a loss in IQ.
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Arnaud73
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« Reply #5 on: May 15, 2006, 08:07:55 AM »
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I may have find one utility that could embed the right ICC profile within my Adobe RGB JPEGs:
http://www.breezesys.com/Downloader/features.htm

Has anyone tryed this utility ?
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Arnaud73
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« Reply #6 on: June 29, 2006, 08:42:32 AM »
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I am still investigating this issue.

I've found another product: EmbedThis! from Colorgrinder (http://www.colorgrinder.com/html/colorgrinder_software.html#ET)

I thought it just did what I was looking for: embed ICC profiles into JPEG files.

I just read the documentation and discovered that this tool uncompress the JPEG file, assign the ICC profile and then recompress the file.

Maybe I am wrong from the beginning: is it possible to embed an ICC profile into a JPEG file without uncompressing/recompressing the JPEG data (like a lossless rotation)?  
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Dennis
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« Reply #7 on: June 29, 2006, 09:39:28 AM »
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is it possible to embed an ICC profile into a JPEG file without uncompressing/recompressing the JPEG data (like a lossless rotation)?
Yes, it is. I don't know how or if there is a piece of software, which does it, but it works. The only thing, which is compressed, is the pure image data. All the informations - especially those, which are necessary for decompression - are written to the header, and thus can be changed. Maybe you want to research at www.jpeg.org or drop a few lines to Guido Vollbeding at www.jpeg-club.org, who wrote some very interesting JPEG tools.
« Last Edit: June 29, 2006, 10:02:58 AM by Dennis » Logged

Best Regards

Dennis.
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