Digital BW, The Print

Hi all:

Here's a mystery (at least to me) that you might help solve.

For some time now, I have been seeing strange geometric artifacts in 
my prints as a direct result of sharpening.  These artifacts are 
generally in the form of parallel bands, but at least once appeared 
as a basketweave pattern.  (This is not microbanding; in fact, it 
can't be discerned through a loupe, only with the naked eye.)  Not 
all prints have them.  They are usually confined to relatively 
limited (but always different) areas of the print; the only common 
element is that they tend to appear in relatively detail-free 
transitions from highlights to midtones, like cloudy skies.  Lastly, 
they occur only when an image has been sharpened, and it doesn't seem 
to matter how the sharpening has been done.  (I get the same thing 
with Nik, PhotoKit Sharpener, Atkinson's edge sharpening macro, and 
plain old USM.)

Ever seen anything like that?  (If I had a flatbed I'd scan one and 
post it for you.  That's another interesting thing:  the artifacts do 
not appear on screen - see exception below - but only in the print.)

Here's the relevant background:  all images are 35mm Tri-X scanned as 
grayscale negatives at 4000dpi, 14 bit files (with 16x resampling) on 
a Nikon 4000, with USM off (at least I think).  They are printed on 
PhotoRag on a 1280.  Until last night, I exclusively used Selenium 
PiezoTones and the plug-in, which I came to blame for the problem.  
To test that, I got some UT's from MIS and made prints using Paul's 
curves and the Epson driver:  same artifacts, except now, for the 
first time, I could see them on screen after Paul's curve had been 
applied.  Also, I have two 1280s, purchased well over a year apart, 
and the problem occurs on both of them.

As you can probably tell, this is driving me nuts.  Any ideas?

Thanks a lot.

Chuck

(Cross-posted to Piezo list.)