More ink = lighter image ?

Question

A question to those who are familiar with
ICC Profile Inspector:
Open for instance EuropeISOCoatedFOGRA27.icc
Choose A2B1, which means A-to-B1:
Input 4 channels CMYK and output Lab.
Rendering Intent Media-Relative Colorimetric
(RelCol).
Choose CLUT
All sliders at the top
Read L*=65280
This corresponds to L*=100
Mapping to paper white has to be done separately
Move sliders CMYK to the bottom, C=M=Y=K=max(100)
Read L*=8418
This should be the darkest rich black
Move the third slider (Y) to the top, Y=0
Read L*=7566
Without yellow ink the surface becomes DARKER.
1. I expect: more ink = less reflected light.
2. Where is the ink limit ?
Any explanations ?
The effect cannot be simulated by Photoshop.
Here we have L*=0 for C=M=Y=K=100, which is
wrong but in a certain sense understandable.
Best regards --Gernot Hoffmann

Answer 1

Hi Gernot.
It's been quite a while since I built profiles for a RIP (I use RGB profiles with my inkjet). If I recall correctly, (and I may not), I used to determine the individual and total ink limits
first, then I linearized using the RIP and my EyeOne after printing a linearization target with the predetermined ink limits. Once the linearization data was read into the software, I printed a profiling target. It also seems to me that I set the TIL in "either" the RIP or ProfileMaker, but not both. Like I said, it has been awhile.
The ISO Coated profile has a white point tag, but no separate black point tag shown in the Tag Table (similar to ProfileMaker). Monaco Profiler has a separate black point tag in the Tag Table.
I looked at a custom press profile a friend of mine made using Monaco Profiler. In the overview, it shows Maximum Black as 11L*, 3a*, 5b*, (not very neutral), but the neutral rendering curve shows a Dmax of only 13.6 L* (perhaps due to inclusion of CMY inks to attain neutrality). So, this suggests that, at least with this profile, Maximum Black does NOT coincide with a neutral black. I am not sure if this is representative of most press profiles or not.
Perhaps this is not a valid comparison, (since it is not CMYK), but I have an RGB profile created by Monaco Profiler (built by a different color management expert). This is for Crane Museo Max matte fine art paper and an inkjet, so the Dmax is low, as expected. The Overview shows a maximum black of 18L, 1a, 3b, but the neutral rendering curve shows a maximum "neutral" black of 20.6L*.
I also have a profile built using ProfileMaker and the identical input data. I was curious how they would compare. (I own ProfileMaker, but do not own Monaco Profiler). It also shows a Max Black of 18L* on the Overview tab of ColorThink, like the Monaco profile, but the neutral rendering curve for RelCol shows 18.8L*.
I'm not sure if this information is helpful, or just adds confusion. It appears Dmax is not the same a the darkest "Neutral" black from inspecting these profiles. I'd guess that the profile is using the Max black instead of the Max neutral black as the Dmax, since it is hard to detect any color toning as you approach solid black.
You can also open both the profile and the reference data in Gretag's free ColorLab (undocumented) to see the input data and the output data. There is probably an easier way.
Lou