Scanner Profiling

[Doug Gray]

Wow!

I'm sticking with my printer made patches for profiling my V850. I don't have Silverfast targets but have compared profiles made with the (small) IT8 target using I1Profiler and ones made with a printed target. There is, as expected, little error (ave dE00 .7) when scanning different printed targets but that can be chalked up to using a common spectro for measuring the printed targets together with virtually no metameric error since the scanned target and crosscheck target were both printed with the same printer.

Further, when I scan both a ColorChecker and the larger SG Colorchecker, the average error using the printed target profile is as good or slightly better than what I get with the IT8 but all were in the low 2's. Not sure how much of that is metameric error v difference in instruments since the CC's were measured with an I1Pro 2 while the printed targets were measured with an I1iSis but I expect some metameric error since the CC's are spectrally different.

I might get some Silverfast reflection targets to test. I would think they would be better than the XRite one which was already 9 months old when I got the scanner.

[Mark D Segal]

Here you go. I do see a LOT of tape popping an error (kind of a meaningless error but one none the less), I see still very low dE reports when several patches are covered with blue tape compared to the one report with NO tape also provided below. That makes me think the report isn't very accurate but it's probably an indicator someone did something wrong. Screen captures below show the dE report and what patches were covered so I hope, self explanatory:

Thanks for doing that Andrew - this is useful. Firstly, it shows that the dE0.7 isn't a fixed outcome, so there is no bug in the software causing it to always report that one value. Secondly, as expected, it shows that when too may patches are taped, the profiling breaks down, which is what I expected. Thirdly, the first two images show that WHERE you place the tape (over the same number of patches) makes a difference to the dE calculation. Not sure why a complete wipe-out of one patch should produce a different error from that of any other. Anyhow, this discussion and your further work on it has produced helpful observations.

[Doug Gray]

Thanks for doing that Andrew - this is useful. Firstly, it shows that the dE0.7 isn't a fixed outcome, so there is no bug in the software causing it to always report that one value. Secondly, as expected, it shows that when too may patches are taped, the profiling breaks down, which is what I expected. Thirdly, the first two images show that WHERE you place the tape (over the same number of patches) makes a difference to the dE calculation. Not sure why a complete wipe-out of one patch should produce a different error from that of any other. Anyhow, this discussion and your further work on it has produced helpful observations.

Yes, thanks Andrew. Most interesting.

The change from .7dE to .9dE is about what one would expect if an additional error of, say 100dE from the 4 taped patches was incorporated in the average. It would be interesting to test the profiles made against each other to see if they resulted in large perturbations around those colors. It's quite possible the software discards them as outliers and produces good profiles even while reporting a higher dE. I can easily test the two if Andrew posts them.