Path: utzoo!attcan!uunet!husc6!im4u!ut-sally!ico!rcd
From: rcd@ico.ISC.COM (Dick Dunn)
Newsgroups: comp.lang.postscript
Subject: Re: PostScript scaling off?
Summary: consider paper expansion
Message-ID: <5270@ico.ISC.COM>
Date: 20 May 88 21:53:59 GMT
References: <313@elan.UUCP> <752@mplvax.nosc.MIL>
Organization: Interactive Systems Corp, Boulder, CO
Lines: 19

> >From this I would expect to get a 5 inch long horizontal line. However, it
> >is actually about 1/32 inch too long. Is it too much to expect better than
> >1/32 inch (~10 pixels or ~0.5%) accuracy,...
...
> It seems that the average Canon printer engine is only nominally 300 dots
> per inch.  All the ones I have seen with Imagen labels have been more
> like 297 x 302...

Even if the print engine could be absolutely precise, you have to take
account of expansion and contraction of the paper--mostly due to humidity.
Normal "copier" paper can easily vary by 0.1" or so in length, which is
about 1%.  With that much variation, (a) what's the point in trying to make
the print engine more precise, and (b) how can you tell, anyway?  In
particular, consider that the printer heats up the paper considerably just
fusing the image--that can shrink the paper a few hundredths (by drying
it).
-- 
Dick Dunn      UUCP: {ncar,cbosgd,nbires}!ico!rcd       (303)449-2870
   ...Never attribute to malice what can be adequately explained by stupidity.