_MG_0126 (TIF)
Flower_06October18_001 (TIF)
In colortheory@yahoogroups.com, DMargulis wrote:
"Also, next month I will be teaching two advanced courses where I am being joined by people who are roughly as good at color correction as I am. If useful images surface before then, we can certainly bring them to that group's attention. For example, Vladimir Yelisseev provided a very useful image on the question of whether to acquire images into ProPhoto RGB."
To which Andrew Rodney responded:
"Here are two .DNG files you can acquire and see what ProPhoto RGB brings to the party. You are welcome to download one or both from my public iDisk (info below).
I acquired both through Adobe Camera RAW using Camera RAW defaults. Bring one in as ProPhoto RGB 16-bit. Bring one in as Adobe RGB (1998) and for torture sRGB. Do a small saturation move (plus or minus) of say only +7 on each, view the images at 100%. What do you see? Try Channel Mixer and other edits that affect color/tone.
Both images were shot at ISO 100 on a Canon 5D but I have another file from Jeff Schewe from a Mark II that shows the same issues in yellows and greens.
Convert the Adobe RGB (1998) file to LAB and do the saturation move too (interesting but requires a conversion getting us back full circle to doing this in 8-bit or high bit). No need for this move if you stick with the ProPhoto RGB file. Additionally, viewing the image in ColorThink shows it clips in Adobe RGB (1998) and that Adobe RGB (1998) is also too small a color space for output to an Epson running K3 inks (the gamut of the inks in useful areas is larger). Have fun."
Andrew has provided two RAW images (a.k.a. "digital negatives") for analysis of the issues involved in digital image capture and RAW processing using Adobe Camera RAW (ACR) and Photoshop, with the intention of producing the highest quality TIFs possible for both archival purposes and for output to large gamut inkjet printers and other devices. When attempts are made to manipulate the images using small changes in saturation or other edits that affect color/tone, these images show significant degradation in both AdobeRGB and sRGB, but not in ProPhoto RGB. Try it and see for yourself.
Andrew's DNG files (the RAW images) can be downloaded from his iDisk here:
http://idisk.mac.com/thedigitaldog-Public
Name (lower case) public
Password (lower case) public.
To help encourage participation by those who may not have or know how to use Photoshop CS2 (and Adobe Camera RAW) to do the conversions, I have uploaded the converted TIFs to my server. Both DNG files were converted using Andrew's ACR settings, which are embedded in the DNG files. Furthermore, because the TIFs are large, I have cropped a 500 x 500 pixel area of interest in each image that will allow everyone to view and discuss the same cropped area of the image without needing to download a huge file. Do note that the ACR settings used for the RAW conversions may not be ideal - if you do RAW conversions, you should do the conversions yourself if you are interested in the effect of the RAW converter settings on the image output. This simply gives everyone a common starting point for sake of discussion.
_MG_0126 (TIF) |
Flower_06October18_001 (TIF) |
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| Full TIF | ProPhoto.tif.zip (67 MB) | ProPhoto.tif.zip (49.1 MB) |
| Full TIF | Adobe.tif.zip (49.3 MB) | Adobe.tif.zip (51.7 MB) |
| Full TIF | sRGB.tif.zip (49.1 MB) | sRGB.tif.zip (52.1 MB) |
| Cropped TIF | ProPhoto-crop.tif.zip (1.4 MB) | ProPhoto-crop.tif.zip (1.3 MB) |
| Cropped TIF | Adobe-crop.tif.zip (1.3 MB) | Adobe-crop.tif.zip (1.4 MB) |
| Cropped TIF | sRGB-crop.tif.zip (1.2 MB) | sRGB-crop.tif.zip (1.4 MB) |
| Cropped JPG | _MG_0126-crop.jpg (61 kb) | Flower-crop.jpg (58 kb) |
The alpha channel used for the crop on the first image can be downloaded here: crop_alpha_channel.psd.zip and for the second here: crop2_alpha_channel.psd.zip
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The gamut of the first image easily exceeds sRGB, as well as AdobeRGB. 
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