Mathematically right values in decomposing to LAB ?

[MarionGaff1]

@Elle

If you upload a similar low resolution scan of the other side (just the scan without any profile), if it would help I would try to make an ICC profile for the scanner using ArgyllCMS, just to see if results look believable without any surprises in the procedure. I’ve never profiled a scanner, but it can’t be that different from profiling a camera.

Here is what I got scanning the other side (200 dpi, no color correction, 48 bits colors, automatic level of exposure is intermediate, Tif format). The same as for the “gray side” : 2 files : one with ICC integrated, one with NO ICC profile

I will use ArgyllCMS later on, as soon as I can find the time to do so, because I have several experiments in parallel