Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!ncar!husc6!cfa!wyatt
From: wyatt@cfa.harvard.EDU (Bill Wyatt)
Newsgroups: comp.sys.next
Subject: Resolution (was: How did they make the printer so expensive?)
Message-ID: <1256@cfa.cfa.harvard.EDU>
Date: 26 Oct 88 15:11:05 GMT
References: <5807@zodiac.UUCP> <17784@glacier.STANFORD.EDU> <1988Oct25.175954.8744@utzoo.uucp>
Organization: Harvard-Smithsonian Ctr. for Astrophysics
Lines: 32

In article <1988Oct25.175954.8744@utzoo.uucp>, henry@utzoo.uucp (Henry Spencer) writes:
> In article <16961@shemp.CS.UCLA.EDU> lange@cs.ucla.edu (Trent Lange) writes:
> >An increase from 300 dpi to 400 dpi is a nearly 80 percent increase in actual
> >resolution, which I call more than slight...
> 
> It depends.  The real question is not how many more dots there are per
> inch, or per square inch, but how much better the output looks, other
> things being equal (which they often are not in comparing different
> printers).  Last I heard, perceived output quality is *not* a linear
> function of resolution.

I agree with Henry, here, but he's used the term `linear' in a way I'd
like to clarify. Yes, 400 dpi versus 300 dpi means 1.77 times the
number of dots per unit _area_. But resolution is generally measured
in lines per millimeter, i.e., in lines per unit length. This means
that 400 dpi is 4/3 the resolution of 300 dpi. It does not mean that
400 dpi will be perceived as 4/3 (or especially 1.77) times `better'
than 300 dpi. 

I suspect the dpi would have to be 3 to 5 times better to look `twice'
as good.

To sum up:
Resolution is a linear function of dots (really, lines) per inch.

Appearence is _not_ a linear function of resolution.-- 

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