Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!wuarchive!decwrl!ucbvax!utzoo.UUCP!henry
From: henry@utzoo.UUCP
Newsgroups: comp.laser-printers
Subject: Re: Apple LW+ axes compressed/stretched
Message-ID: <8912020335.AA21307@crayola.cs.UMD.EDU>
Date: 15 Nov 89 22:57:23 GMT
References: <8911150343.AA03467@crayola.cs.UMD.EDU>
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>... the x-axis is stretched a little and the y-axis is
>compressed a little.  But on a real PostScript typesetter
>(a Linotronic L300) the measurements are perfect.

The problem here is that the manufacturer of the printer couldn't be
bothered to get it spot-on.  The y-axis resolution is determined by
the relationship between paper motion and laser scan rate, and usually
is fixed by the print engine.  The old Canon engine (which is what's
in the LW+, LaserJet, etc etc.) was close to 300/inch but not dead on.
I haven't checked the new Canon engines.  The x-axis resolution is set
by the "video" rate from the printer controller board.  This is normally
set by a crystal oscillator on the board.  Many manufacturers prefer to
use a standard oscillator that's almost right rather than paying for a
custom part that exactly matches the y-axis resolution.

If you're willing to spend some money and void your warranty, you can
change oscillators to make the x-axis match the y-axis.  Nothing you
can do without a lot of machine-shop work will change the y-axis.

Typesetter manufacturers generally have a fussier audience -- the printing
types who reject output for flaws visible only under a magnifier -- and
more money to spend on getting things just right.

                                     Henry Spencer at U of Toronto Zoology
                                 uunet!attcan!utzoo!henry henry@zoo.toronto.edu


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