Path: utzoo!attcan!uunet!mcsun!cernvax!chx400!sgzh!root
From: root@sgzh.uucp (Bruno Pape)
Newsgroups: comp.sys.sgi
Subject: Re: How Many Gray Scales On Laserwriter II NTX?
Message-ID: <1990Mar26.134330.12298@sgzh.uucp>
Date: 26 Mar 90 13:43:30 GMT
References: <5890597@um.cc.umich.edu>
Reply-To: root@sgzh.UUCP (Bruno Pape)
Organization: Silicon Graphics S.A., Zuerich, Switzerland
Lines: 27

In article <5890597@um.cc.umich.edu> Tim_Buxton@UM.CC.UMICH.EDU writes:
>
>         We are using the icut and tops commands to take grayscale images 
> from the screen and send 
> them to an Apple Laserwriter Plus NTX.
> We are getting  very "stair stepped" halftones.  That is,
> where a standard ramp is displayed on the screen varying
> smoothely from dark to light, the LaserWriter image will
> show a series of discrete bands.  The reason for this 
> evidently is the half-tone process. 
> 

Yea, I have had the same problems on both a LaserWriter II and a
QMS ColorScript 100, and the problem seems to be with the half-toning.  

I think the problems lies with the default spot function that is provided
for the default screen definition, my guess that it is a compromise
between speed, memory, and beauty.

If one were to fully understand Program 15 / Filling an Area with a Pattern,
in the PostScript Language Tutorial and Cookbook one might have a better
idea of how to get better half-toning results.

I never did understand it well enough though.  You might try posting to
comp.lang.postscript.

Bruno Pape