twenty_one, thanks for the feedback.
Some tests show: Grayscales based on any gray profile, if converted to CMYK, deliver rich black.
This is so even for the black-ink gray profile.
It is possible to create a gray image in CMYK with K-only directly (without pasting a gray channel into the K-channel):
1. Color Settings > ISO Coated v2 (eci) > Custom
2. Choose Black Generation GCR with max.Black according to the image below.
3. Image Mode > Grayscale
The calculation is merely based on ink (here european ink), not on a previous profile. Therefore I've chosen
15% dot gain instead of the default value 9%. Thus this workflow is not entirely consequent.
Lab values are preserved, as shown. Channels CMY are empty, as required.
Printing PDF documents with RGB, CMYK, Gray and Lab components by RIP (raster image processor)
is not simple and affected by not embedded gray profiles (coming from InDesign):
http://docs-hoffmann.de/riptest05072013.pdf
Best regards --Gernot Hoffmann
Is it really not possible to edit such a post here after posting?