Digital BW, The Print

I have to agree with the notion that something else is at work here.

I have observed the same phenomena in some of my prints.

My theory is that larger areas of a similar tonality that occur near 
where the ink tonality part ions
are causing this "flatness" and then a sharp tone break.
These are not going to be able to be observed in the file on screen and 
so far I cannot predict
when it's going to happen.
I first saw this is some photos I was working on for a very excellent 
corporate shooter who was doing
16x20's of the principals of some company.
The negs and scans had tons of rich tonality and detail and we were 
 getting, like flat areas where the leaves
in a tree where all upper mid tones.
I was able to fix this by making drastically vertical curves in just the 
area on the curve where this weird
flatness showed up, thus stretching the local contrast and everything 
resolved itself.

Since then I've seen it in lots of pictures and not just from my studio, 
and in other tonalities as well.

There are three places where the piezo software, or any curves based 
partitioned workflow for that matter,
must start to add in the next darker ink. and I believe that point is 
where this effect occurs.

One thing that I have done that has given me insight is that I print a 
file that includes the ole 21 step wedge
through different  Paper ICQ's.
This shows clearly that the breaks between inks is happening at 
different places in the tonal curve, and
that appropriate mis-matching of "profiles" can be very useful.

J.Z.