The uselessness of scanner profilesI figured it was time to circle back to this thread. This was my first posting to this forum, out of frustration and desperation after months of trying to figure out what I was doing wrong. Then I took a step back and made sure my fundamentals were correct before continuing on. For anyone that's interested, I took what I learned and all my trial and error techniques and finally put together a concise analysis of some of my scanner profiles. I'm sure to the pros out there that this is nothing new, but I found it to be an extremely clear way of showing the problem I'm facing and might help some other amateur like me not waste too much of their time.
Applying an ICC profile back to the scanned image that created the profileLet's start with the classic IT8 target that's bundled with a lot of higher-up scanner packages. I have three of them, one from LaserSoft, two from Wolf Faust (one Fuji, one on Kodak). They all give me the same results FYI. This example uses one from Wolf:
(Click for larger image.) On the left are the RGB values of the scanned target using Epson Scan with No Color Management. (I sampled the RGB values from the scanned image as a color list.) I created an ICC profile using i1Studio and applied it to the RGB values with an absolute rendering intent, resulting in the LAB values in the next column. Moving on are the LAB values from the IT8 reference file provided with the target. The final column are the dE2000 values between the profiled image and the reference values. Green are <= 1dE, yellow up to 2.5dE, etc.
Here's the similar results from a ColorChecker 24 and a Digital ColorChecker SG. (Note that I made my own reference files because there were a few significant deviations between my targets and the bundled i1Studio reference files.)
All this does is confirm that the profiling software can correct for the scanned target itself, but that's something. Presumably, that means my equipment and software are working and that my workflow isn't just wrong.
Applying a profile from one target to anotherThis basically fails. I'll share two that I thought were interesting because they kinda backup my original observations with the color shifts.
First, a scanned IT8 with a profile from the DCCSG. There are obvious color shifts in the greyscale patches.
Second, the DCCSG with the IT8 profile. It's harder to see but the greys and blacks took on a greenish cast. The LAB values would seem to confirm it. Plus the dE values are way out there anyway.
So, I'm sure in hindsight this should be obvious. All three targets I'm working with have different spectral characteristics. This leads to my prints…
Applying the profiles to a printed photoI took an image of the ColorChecker 24 from BabelColor that was already in LAB colorspace and printed it using an absolute intent to a custom paper profile also made with the i1Studio. I measured the print with my i1Studio spectrophotometer and did the same tests. The only profile that did a good job was a custom target of 962 patches that I made with Argyll
on the same paper. The other targets weren't good enough.
The ColorChecker profile couldn't even correct the printed ColorChecker:
Custom Argyll target:
For all I know this could be even better if I made sure to have the same print settings.
Conclusion of the testingSo this seems to prove what was said before by Doug, Graeme, and others that are much more knowledgeable about this stuff. But I'm happy that I proved it to myself. That said, now I'm kinda annoyed. Scanner profiling is marketed as a simple solution to getting your colors right and it's clearly not. I'd feel ripped off if it weren't for the fact that the i1Studio has worked for print profiling and display profiling. Glad I didn't spend big bucks on third party scanner profiling software. I did spend a ton of time with Argyll and got similar results to the i1Studio in the end. But Argyll is awesome and I couldn't have done these tests without the other tools it provides like its spotread tool – because the i1Studio doesn't offer that capability. You can see all the test results
here.