Mike,
thanks for the tests.
Again: the odd gamut warnings appear for all rendering intents. But for the moment we can leave it at that.
My opinion about RelCol and AbsCol:
The viewing light for print products is D50. Therefore the reference white for the PCS CIELab is D50 as well.
If the RGB space is defined for D50, like ProPhoto, then AbsCol and Relcol is the same.
If the RGB space is defined for D65, like sRGB, then
AbsCol and RelCol is different. It’s just the coordinate transform of the D65 gray axis to the D50 gray axis.
Essentially, AbsCol isn’t intended as a printing space.
For me it´s the rendering intent for CMYK–CMYK conversions for proof printing.
That means: the final gamut RelCol is valid. Source CMYK is converted to Lab and Lab is converted to destination CMYK. The output profile (inkjet) was made for RelCol. The conver- sions are done without white point shift (AbsCol)
This is so far valid without taking paper white into consi- deration.
RelCol can apply corrections for paper white, but this is IMO (and in my practical experience) rather doubtful.
Much more important than paper white is IMO the black point compensation, which is often applied in Perceptual, but in a somewhat unspecified manner. RelCol doesn’t have a BPC
by ICC standards.
PhS RelCol with BPC is often similar to Perceptual.
Here is my attempt how to decipher the ICC specs:
http://www.fho-emden.de/~hoffmann/cmsicc08102003.pdf Comments and corrections are welcome, maybe by private e-mail.
Best regards –Gernot Hoffmann