Mathematically right values in decomposing to LAB ?

[MarionGaff1]

@Elle

I did make several different types of ICC profiles for your scanner using the reduced-size target chart you uploaded. I’ll try to post some images and the relevant commands later today or more likely not until tomorrow morning (US east coast time).

Thank you so much!

@Elle

It would be good to put a piece of black paper behind the chart, large enough to cover the scanner bed. It might not matter for a scanner - I just don’t know. But for a camera, surrounding the target with white just causes camera “veiling flare” - I think that’s the right term. So to be on the safe side it might be better to just eliminate the possibility by using a black background behind the target chart.

Also, speaking of the white background, I measured a small amount of difference at one end of the background vs the other end, around L=92-93 at one end, down to L=89-90 at the other end. I’m not sure how much this might affect results, but maybe flat-fielding - again, something I’ve never done - before making the ICC profile might be a good idea. The fall-off in intensity seems uniform and consistent for all the various scans.

On the other hand, maybe flat-fielding would be more trouble than it’s worth. It might be interesting to put the target in the center of the scanner and scan it twice, spinning it 180 degrees for the second scan, and comparing resulting ICC profiles from each scan.

Here are the scans that I obtained without ICC profile integrated.
I still did not figure out if I should register my scans with ICC profile integrated or not.
If I register all my scans with ICC integrated, then I will not be able to “replace” the ICC profile integrated by the scanner by my own “customized” ICC made with the target chart OR are the ICC profile integrated by the scanner and the image “glued forever”?
If I understand well what ICC profiles are, they are made to give information about the frame of reference to use to interpret properly the coordinates that define each color.
So, if I don’t integrate any ICC profile, how are the softwares able to open the scans with the right colors (right colors being information given by the scanner).