Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!csri.toronto.edu!mccool
From: mccool@csri.toronto.edu (Michael David McCool)
Newsgroups: comp.graphics
Subject: Colours
Message-ID: <1989Nov14.090210.22777@jarvis.csri.toronto.edu>
Date: 14 Nov 89 14:02:10 GMT
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With respect to shades of grey: 64 SHOULD be enough for monochrome, if
you adapt the distribution of levels to the "gamma" curve of your monitor.
This will probably be a nonlinear distribution.  And yes, I have done
this (not on the VGA; we do medical computer graphic reconstructions with
big CAD/UNIX type systems).  You might also want to adapt the colour map
to the image, such as providing the most colours around the highest probability
colour.  256 levels gives you plenty of brute force, which works, of course.

Purists will probably complain that with their eye 1cm from the monitor they
can see a difference; but I can't.

If you add colour, your discrimination goes up.  One trick used in reading
things like CAT scans, which have very subtle grey scale, is to use a "thermal"
scale, with white as the brightest and dark orange at the low end of the
scale.  This REALLY improves discrimination, because you change colour and 
brightness at the same time.  

So if your goal is reading subtle grey-scale images, try colour!