QTR-Quadtone RIP

I am having a big problem trying to create a profile for Epson Premium Photo Gloss.

Every time I set an ink limit, regardless of value, when it comes to measure a 21 step wedge for linearisation, I find that the last two (darkest value) steps appear to have lower density values than the lighter steps.

It seems that somehow there is a feedback problem within the process I am using, but I can't imagine where this may be.

For example:

Printing out the inkseparation6.tiff file via QTR print, with no color management I measured density values which indicated an ink limit of 75%.  I then reprinted the inksearation6.tiff to calcualate the gray value, which was 35%.  I was using Cyan, Cool Photo black and Light Cyan, Dilute cool photo black, to get a cool profile.  

I then install the profile, without linearisation details.  Next, when printing a 21 step wedge to linearise the profile, I then find that the maximum density value is about 90% and declines for the next two steps.  I have repeated all these steps several times and have even gone down to an ink limit of 45%.  However every time I've tried to create a linearisation file I find that the darkest steps have a density value lower than 90%, which seems to have the maximum value.

The advice from tutorials suggests to set the ink limit at the point where the initial density values reach a maximum. I.e. if the measured density values are 2.00 at 60%, 2.01 at 65% 2.01 at 70%, then 65% should be the set ink value.  Initially I followed this procedure to set the max ink value.  I now think that instead of aiming for the maximum density value, I should go for the maximum density value reached by steps of .02 instead of 0.01. so if the steps go up such as, 2.00 for 50%, 2.04 for 55%, 2.05 for 60%, 2.06 for 65%, 2.07 for 70% 2.08 for 75%, I should set the ink limit at 60% and no higher.  However, following this rule, when it comes to linearisation, I find that the top one or two density values are still lower than 90 or 95%.


It is getting beyond frustration point now.  I think the next step is to remove all programmes and start afresh.  I seem unable to get to the point of linearisation, so would appreciate any help.

Ross