[comp.lang.postscript] Banding problem with 24-bit colour PostScript

bjnw@castle.ed.ac.uk (B Wylie) (11/27/90)

Recently I was involved in the evaluation of several colour PostScript
laserprinters for the University of Edinburgh.  For the requirements of
the various drafting packages available, pretty much all the printers
were indistinguishable regarding printed image quality.  However, the
needs our researchers were for colour pixmap dumps, and for this purpose
I was using the pbm+ image manipulation package, and a little widget
written to interface our (peculiar) image format to the ppm standard. 

With 8-bit images, the colour output was again excellent --- tho'
printing times were annoyingly lengthly.  Our problem was with 24-bit
images, which exhibited very noticable colour banding --- like the
half-toning banding evident on monochrome output.

I'm wondering whether this is a limitation in the printers or arises
from my misinterpretation of the use of the pbm+ toolkit.  Any
suggestions as to any obvious error on my part, or for possible
solutions would be very welcome, as indeed would information regarding
the location of 24-bit colour PostScript test files which might not be
prone to this problem.

  Slainte,                 "Let he who hath understanding reckon the number of
    Brian.                  the \baselinestretch ..." --- The Book of Lamport