Path: utzoo!attcan!uunet!lll-winken!lll-lcc!ames!ncar!gatech!bloom-beacon!athena.mit.edu!mar
From: mar@athena.mit.edu (Mark A. Rosenstein)
Newsgroups: comp.lang.postscript
Subject: Re: I need a finer setgray
Message-ID: <8610@bloom-beacon.MIT.EDU>
Date: 4 Jan 89 19:07:26 GMT
References: <21801.1989Jan3.12:29:38@hammer.me.toronto.edu>
Sender: daemon@bloom-beacon.MIT.EDU
Reply-To: mar@athena.mit.edu (Mark A. Rosenstein)
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Organization: Massachusetts Institute of Technology
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In article <21801.1989Jan3.12:29:38@hammer.me.toronto.edu> eastick@me.toronto.edu (Doug Eastick) writes:
>
>At a distance the gray looks fine, but up close (it's for Dept.
>letterhead) the black dots are too big.

The halftone screen used is defined by three parameters, the frequency
(dots per inch), angle (how the rows of dots line up), and a procedure
which determines the shape of the dots.  You can retrieve the current
values of these parameters with the currentscreen operator, and set
new ones with the setscreen operator.  For instance, the code fragment

	currentscreen 3 -1 roll 2 mul 3 1 roll setscreen

will double the number of dots/inch used.

HOWEVER, be warned that there is a reason the default was set the way
it is.  Finer dots may not print well in your print engine, and will
likely not copy well in a copier.  The default frequency is different
from printer to printer, and you will have to experiment some to see
if you can increse that frequency and still have output that looks
good.

A better solution is to design the logo so that you are happy with it
in draft form, then put a copy of that postscript file on a floppy and
take it to a typesetting service that has a real phototypesetter which
speaks postscript, such as a linotronic.  The same postscript file
printed on a phototypesetter instead of a laser printer will have a
much finer halftone pattern.  This output will be of a quality
suitable to use as a master for offset printing letterhead, as well.

					-Mark Rosenstein
					mar@athena.mit.edu

		 Variable won't and Constants aren't.