Path: utzoo!attcan!uunet!munnari.oz.au!uhccux!ames!ncar!ico!rcd
From: rcd@ico.isc.com (Dick Dunn)
Newsgroups: comp.lang.postscript
Subject: Re: compensating for distortion
Summary: nothing so nefarious
Message-ID: <1990Jun1.155110.3330@ico.isc.com>
Date: 1 Jun 90 15:51:10 GMT
References: <90May30.095014edt.18974@me.utoronto.ca> <1289@chinacat.Unicom.COM>
Organization: Interactive Systems Corporation, Boulder, CO
Lines: 41

woody@chinacat.Unicom.COM (Woody Baker @ Eagle Signal) writes:

> 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...

Foo.  I just ran a copy on a relatively high-end copier to check.  It is
1:1 on both axes to within better than 0.5%.  That's greater accuracy than
the dimensional stability of paper.

The real reason most copiers tend to be off a little is very simple:  They
enlarge ever-so-slightly to compensate for positioning error and variation
in paper size, so that you don't see a black line around the extreme edge
of the copy where the edge of the original was.

Laser printers do (as Henry noted) commonly have a pixel aspect ratio not
quite 1:1.  But if you're really concerned about that, you can take some
precise measurements and compensate with a transformation matrix, or if
it's an image, compensate in the scanning or conversion.

>...Especialy color copiers.
> They would not release color analog copiers period...

What's a color analog copier?  I'm assuming you mean a copier that is
capable of continuous-tone repro (as opposed to high-contrast "line" copy).
What ever would that have to do with counterfeiting?

>...You will note that
> all of the current color copiers use a glossy toner.  Also mandated by
> the treasury department. 

No, mandated by the process.

What about standard one-color copiers with a selection of toner colors?

Conspiracy theories are fun, but sheeesh!
-- 
Dick Dunn     rcd@ico.isc.com    uucp: {ncar,nbires}!ico!rcd     (303)449-2870
   ...Simpler is better.