If what I've read is correct, maybe Coca was seeing that incorrect sRGB tag and it caused your faulty profile.
I'm reasonably certain the Coca ignores embedded profiles because, as a test, I generated two profile from a scanned target, one with and one without an embedded profile and the Coca profiles came back the same (as far as I could tell by applying them to an image).TESTING PROFILES
I've been thoroughly putting Coca through its paces and have found some anomalies. This is what I have done:
A. Scanned a Kodachrome IT8 target at 2000 dpi, 14-bit, with seven different settings…
1. CM off, Gamma 1.0
2. CM off, Gamma 1.5
3. CM off, Gamma 1.8
4. CM off, Gamma 2.2
5. CM on, Adobe RGB (gamma 2.2, embedded profile called Adobe RGB
6. CM on, Apple RGB (gamma 1.8, embedded profile called Apple RGB
7. CM on, sRGB (gamma 2.2, embedded profile called sRGB
… and gave the resulting images names such as Kodachrome IT8 Gamma 1.0
, Kodachrome IT8 Adobe RGB
, and so on.
B. I saved the targets without
C. I generated 4 profiles for each target, using these options in Coca: Lab, XYZ, Gamma+Matrix, Shaper + Matrix, and gave the profiles names such as: Kodachrome IT8 Apple RGB XYZ
. The name reflects the way the target was scanned, and the way the profile was generated. There are 28 profiles, generated at high quality, and two generated at ultra-high quality to see if there was any difference (there wasn't).
D. Then I chose five of my test slides (slides that are a challenge to scan) and scanned each of those with the seven settings given in A. The images had names such as: Ref 02 Gamma 1.0
, Ref 05 Apple RGB
, the name reflecting the slide number and the scan method. This gives me 35 images with which to test the profiles.
E. Then starting with Ref 02, I opened the seven scanned versions of Ref 2 in PS – I had seven tabs open, each tab showing the same image but scanned a different way.
F. Then for each tab, I applied the four profiles applicable for that image, compared them, and took notes. So, for example, the first tab might have been Ref 02 Adobe RGB
(scanned with Adobe RGB), and then I applied the profiles: Lab, XYZ, Shaper and Gamma to see the effect. Then I moved to the next tab, and repeated, until all seven versions of Ref 2 had been compared.
G. Then I closed all the Ref 2 images, and opened the seven Ref 5 images, and applied four profiles to each.
A pretty thorough test to determine which profile worked the best. And one did work the best – and it wasn't Gamma 1.0.RESULTS OF TESTS
Something very interesting turned up: with CM off, the profiles resulting from Gamma 1.5 and Gamma 2.2 scans of the IT8 target generated nonsense profiles in Coca. When applied to the appropriate image, nonsense colours appeared. Any suggestions why? Gamma 1.0 worked, Gamma 1.8 worked, Adobe RGB worked … but not Gamma 1.5 and 2.2. Same scanner, same process, same profile generator, same application to an image, but nonsense results.FILES TO REPLICATE MY TESTS
Just in case anyone wants to try and work out what went wrong I have uploaded all that is needed to replicate my testing. Coca is free, so if you've never used it, here is your chance. In this folder, http://www.mediafire.com/?thogddgfozxi2
, can be found:
• Coca installation file (Coca_setup.exe
, 10.7 MB)
• 7 IT8 scans + data file required by Coca (Kodachrome IT8 Targets.zip
, 14.8 MB)
• 7 Kodachrome scans (Reference Scans.zip
, 11.5 MB)
• 30 profiles, 28 at high quality, 2 at ultra high (Kodachrome Coca Profiles.zip
, 6.7 MB)
To reduce file size, the IT8 scans have been resampled to 1000 dpi, 8bit (from the original 2000 dpi, 14-bit). This resampling has no effect on generating profiles, as far as I could tell when I re-profiled some of them at the reduced resolution.BANDING
If you want to see the banding problem, check out the deep blue of the water in the foreground of the Kodachrome scans. Banding is subtle, but definitely present in all images except Gamma 1.8. It was present in most of the other reference images as well, to various extents. The slides I have chosen as reference slides are a serious challenge to scan. They show extreme contrast, or gentle gradations, or saturated colours against other saturated colours. Most scanners do a reasonable job scanning an "easy" slide – and you won't see banding – but I've dived in the deep end.COCA HELP
If you need help with Coca, the home site is here: http://www.nla.gov.au/preserve/dohm/coca.html
. You do need to put a sensible name into the "Internal Profile Description" field (Section 7), because that is what appears as the profile name in PS. I ran Coca from Windows XP. I don't know if it works on later versions.