I am using Silverfast to make a scan and save it as CIE-Lab. I set Absolute Colorimetric rendering intent in Color Management System preferences, calibrated the scanner, then scanned some white paper with known Lab values close to [100, 0, 0]. When I used Photoshop to look at the file’s Lab values, they were [100, 0, 20] or light yellow! I then switched to Relative Colorimetric rendering intent, redid the scanner calibration, and re-scanned the sample. This time the Lab values were correct: [100, 0, 0]. Some questions:

  • Why is Relative the right choice, not Absolute, when saving CIE-Lab values?
  • Why does rendering intent affect Lab values, which are device independent?
  • Are there any other changes I should make to the following set of CMS preferences if I want to save correct Lab values?

Input -> Working Space: Image Color Matching
Working Space -> Monitor Image Color Matching
Working Space -> Output CIE-Lab
Input: my scanner profile
Internal: Adobe RGB
Gray: None
Ouput/Print: None
Rendering Intent: Rel. Colorimter
Embed ICC Profile: Box is checked
Profile to embed: None

[Sorry I couldn’t upload a screenshot. Imgur is having a problem].