Two calibrated flatbed scanners with different reading on the same color, where is the problem coming from?

Question

I'm collaborating with another person on scanning anime cels. But first we need to confirm that our scanners produce identical colors. So we picked one paint color that we both have and compared our scans.

I'm using an Epson Perfection v600 scanner, while my partner uses an Epson Expression 10000XL. We both calibrated our scanner using the Silverfast scanning software 8.8 with a 864 patches IT8 target. And our average deltaE are 0.6 and 1.0, which mean our scans should be color accurate.

However our testing scan on the same paint color looks noticeable different. Our hues are 243 to 233, that's enough difference to tell something is wrong. But I couldn't figure out where the problem came from.

Update:

For more testing, we both make a scan of our IT8 target under our calibrated profiles and saved under ProPhoto RGB color profile. When checked for proofing in photoshop, the gamut of my scan was within the AdobeRGB range but my partner's scan, many of the patches exceed AdobeRGB.

I uploaded my scanned target here. Target 1 is mine, target 2 is my partner's.

https://i.stack.imgur.com/Pp1os.jpg

Answer 1

If you are getting the same readings from the same colors on authentic IT8 calibration charts, then the problem is likely something to do with the "paint we both have" and not the scanners.

Batches of paint are not exactly alike; and was the paint applied to exactly the same color/brightness of substrate; at exactly the same thickness/density?

Answer 2

First of all, a hue difference alone is not meaningful because it's an angle revolving around neutral grey (achromatic). For a color of low saturation (near grey), you can have a large hue offset that will result in a very small delta E at the end, because both records will be very close from achromatic (so, large angle with small radius). The only meaningful way to compute the difference between 2 colors is using the delta E.

Then, from your scans, I can see that the target #2 has a warmer grey, so I guess the first issue is with white balance. The expected result of this is more saturated reds and oranges, less saturated blues. But the target #2 is more saturated everywhere, so there is more likely another problem on top.

The fact that both scanners may not have the same gamut changes nothing to the output. In theory, it could, but both your targets are printed on Fuji Crystal Archive Supreme, which is a photochemical paper that will not be able to print colors far outside of Adobe RGB. Whatever gets printed on this paper will most likely fall inside both scanner's gamut.

I would probably check into the profiling software used, and how it is configured.