QTR-Quadtone RIP

I decided to start calibration from scratch on some of the 'glossy' 
papers I have (Innova Fibre Print White Gloss, Hahnemuhle Photo Rag 
Baryta, and Permajet Fibre Base Royal). I'm using a PC with Windows XP 
and QTR 2.7 (with the necessary patch!) Epson Pro 3880 and the standard 
Ultrachrome K3 VM inks.

I ran the first calibration prints using 1440 dpi unidirectional with 
adaptive hybrid dither (which is what I've usually used for printing 
with prebuilt curves), and for the first paper I was printing did a 
second print using 2880 dpi to see if there was any density difference). 
When I'd done the prints for all three I went back to the first to 
compare the 1440 and 2880 prints which had time to dry a little.

There's no obvious difference at the dark and light ends of the scale, 
but there is in the middle - for the 2880 dpi print for each ink there 
was very little visible difference between the 45 and 50 patches. On the 
darker inks there's little visible difference anyway, as the inks are 
reaching their maximum density by then, but the lighter inks continued 
ton crease in density from the 55 patch onwards. The 1440 dpi print 
behaved as one would expect on the prints both before and after this one 
- there is a gradual progression 45-50-55 with each being distinct. I 
then made a 2880 dpi calibration print for the Permajet paper, and this 
too showed the same problem, so it appears to be a general problem 
printing at 2880 dpi rather than a wierd paper glitch.

has anyone else seen a similar problem with 2880 dpi?

-- 
mike finley photography
http://www.mikefinley.co.uk