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From: BNB@MATH.AMS.COM (bbeeton)
Newsgroups: comp.laser-printers
Subject: Re: compensating for distortion
Message-ID: <9007120321.AA28454@crayola.cs.UMD.EDU>
Date: 22 Jun 90 18:35:41 GMT
References: <9006190354.AA22032@crayola.cs.UMD.EDU>
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on 30 may, andy sun anu-guest asked about distortion suffered on an
apple laserwriter ii nt when he tried to print a square.

i'm neither a postscript programmer nor a regular laserwriter user,
but recognizing distortion is important to us at the american math
society when we are implementing document designs in tex.  we
discovered that the old laserwriter guarantees no more than 2%
distortion; that's about 3pt in 2in, and the greater the distance, the
more noticeable the discrepancy.  to determine the exact behavior of
the particular machines we're using, we developed a test in which
several rules run horizontally and a similar group of rules vertically.
(the pattern we chose is 4 parallel rules of nominal 3, 4, 5 and 6in.)
we then print the same file in both portrait and landscape mode, and
lay them one on top of the other on a light box to see what's happening.
this doesn't solve the problem, but it does very quickly let us know
the degree of variation.  and if it's more than 2%, we can yell at the
hardware maintenance folks.

the only device we've had come in right on the money is our typesetter
(an aps micro-5).  a machine based on the xerox xp-24 engine can be
tuned so that it's under 1 pixel off in 6in; unfortunately, it's a
write-white engine and has worse problems on that account.  a couple
of ricoh engines do reasonably well.  sad to say, the laserwriter is
the worst of the lot, and 2% is really an unsatisfactory degree of
variation for graphic arts purposes.  but maybe, after you find out
what the reality of your machine is, you can find a hardware competent
who's willing to tune it tighter than the promised 2%.  good luck.
						-- bb
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