Path: utzoo!attcan!uunet!mtxinu!jaap
From: jaap@mtxinu.COM (Jaap Akkerhuis)
Newsgroups: comp.lang.postscript
Subject: Re: compensating for distortion
Message-ID: <1237@mtxinu.UUCP>
Date: 1 Jun 90 18:24:53 GMT
References: <90May30.095014edt.18974@me.utoronto.ca> <1990May31.001233.9322@utzoo.uucp> <1289@chinacat.Unicom.COM>
Reply-To: jaap@mtxinu.UUCP (Jaap Akkerhuis)
Organization: mt Xinu, Berkeley
Lines: 58

In article <1289@chinacat.Unicom.COM> woody@chinacat.Unicom.COM (Woody Baker @ Eagle Signal) writes:
 > In article <1990May31.001233.9322@utzoo.uucp>, henry@utzoo.uucp (Henry Spencer) writes:
 > > In article <90May30.095014edt.18974@me.utoronto.ca> sun@hammer.me.UUCP (Andy Sun Anu-guest) writes:
 > > >because of the aspect ratio (does a laser printer have aspect ratio?) of the 
 > > >laser printer? ...
 > > 
 > > Almost certainly that's the cause.  Most "300dpi" laser printers are in
 > > 
 > > (This isn't unique to laser printers, either:  most photocopiers likewise
 > > have slightly different X and Y axes.)
 > 
 > I used to work for a place that sold Copiers.  I sold Lasers, and Computers.
 > I was told by people whom I trust, that NONE of the photocopiers would
 > produce an exact 1 for 1 copy.  It was always about 3% off.  This (or so
 > I was told) is because the treasury department didnot want anyone copying
 > anything exactly, for fear of counterfitting.  Especialy color copiers.
 > They would not release color analog copiers period.  You will note that
 > all of the current color copiers use a glossy toner.  Also mandated by
 > the treasury department. 

I've got the feeling about yet another urban legend being born.

Copiers usually enlarge 2 to 3% for the simple reason that it makes
the life of the designer/manufacturer coping with various tolerances
of papersizes etc. much easier. Note that you deal with paper moving
around. If you want make an exact copy, you have to make sure that
the original and the paper you copy to is on exactcly the right
place, else it is very easy to have light from the edges op the
original show up at the copy. Furthermore the original might not
be exactly up to spec in size, so again one would see this edge
anomalies. For an experiment, try to make an exact 1 to 1 print of
a negative using an enlarger.  You'll be suprised how hard it is
compared to a direct contact print.

I don't know about the glossy color toner, but in general glossy
surfaces look brighter then non-glossy ones. That might make
producing color copies easier.

It would be very silly of any treasure department trying to control
the copier industry out of fear of forgeries. That would immediately
start an interesting market of illegal machines.

Back to the original subject. I too have experienced that the aspect
ratio of various printers (and typesetters for that matter) is not
constant.

But why are 300dpi printers not 300 in general? At the introduction
of the Agfa P400 they told me the next story:

Their printer is marketed as a 400 dpi model, but if you really
look in the specs, it is actually something like a 406 dpi.  The
406 dpi make a nice figure in a metric system.

H'm, if you get your calculator out you can see that that doesn't
make a lot of sense, so it might be yet another urban legend.


	jaap