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Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!cs.utexas.edu!uunet!omen!caf
From: caf@omen.UUCP (Chuck Forsberg)
Newsgroups: comp.periphs,comp.sys.ibm.pc
Subject: Re: High resolution monitors
Keywords: resolution dot-pitch eyestrain
Message-ID: <820@omen.UUCP>
Date: 31 Jul 89 20:14:54 GMT
References: <1989Jul29.234145.24136@psuvax1.cs.psu.edu>
Reply-To: caf@omen.UUCP (Chuck Forsberg)
Distribution: usa
Organization: Omen Technology Inc, Portland Oregon
Lines: 34


I've worked out a rule of thumb for discussing resolutions to
use with color monitors with shadow masks, based on the
Nyquist sampling theory.  According to the Nyquist theory, we
need to sample at 2*frequency to accurately represent
1*frequency.  Applied to my Diamondscan monitor I get:

        240 mm horiz display length / 0.28 mm dot pitch = 857.

So it can handle 428 lines of resolution without losing much
information.  Since most fonts on 640x480 are two or more dots
in feature size, we can fudge some; 640x480 text "looks good".
But these numbers suggest that increasing the digital
resolution beyond 640x480 isn't going to allow for that much
more information.  At 800x600, small font X-Windows text gets
rather hard to read (the "micro" font is illegible).  If you
want to get the best out of resolutions above 640x480 you need
a larger screen and/or a finer dot pitch.  That's why
"serious" CAD monitors have many more dots on their screens
(and cost many arms and legs too.)

An 800x600x256 rendition of day.gif or mrlake.gif (Mirror
Lake) is mighty impressive, more so than most 640x480x256 pix
I have.  Translation: you can bust the minimums on pictures
but not on small font text.

So when selecting a monitor, consider the number of dots on
the physical screen as well as more traditional measures of
resolution.

A final rule of thumb: if you can see the dot pitch on a
monitor, it's too big for your viewing distance.  Use a
smaller dot pitch, move away from the screen, use glasses with
last year's prescription, or smoke more dope.