Newsgroups: comp.arch
Path: utzoo!utgpu!watserv1!watcgl!imax!dave
From: dave@imax.com (Dave Martindale)
Subject: Re: Resolution, etc.
Message-ID: <1990Nov15.052925.1265@imax.com>
Organization: Imax Systems Corporation, Oakville Canada
References: <240@csinc.UUCP>
Distribution: na
Date: Thu, 15 Nov 90 05:29:25 GMT

In article <240@csinc.UUCP> rpeglar@csinc.UUCP (Rob Peglar) writes:
>
>Point was - resolution of 1kx768 is not a big win for *imaging*.  Yes,
>the subject was images, not text, not multiple 80x25 windows, not see-how-
>many-characters-we-can-cram-onto-one-screen stuff.  

>As for television, I used it as an analogy to prove that *color* was the
>important aspect of imaging, not *resolution*.  I received a piece of e-mail
>which compared TV to "a crinkled piece of sh*t" as far as resolution goes.
>Again, I agree.  The original analogy is still valid. (I think)

What exactly do you mean by "imaging"?  I think it means looking at
photographic-quality images.  For that, you need decent resolution
in *both* colour and space.

Television does manage to encode three colours with pretty good colour
resolution, over large areas.  You need a 24-bit frame buffer to
match it in the digital world if you're going to store the information
as RGB.  But television's spatial resoultion is simply awful.
It's capable of resolving only about 50 "pixels" horizontally
for certain combinations of alternating colours.

Television works amazingly well, considering the tiny bandwidth it has
to work with, when viewed from a distance of 5 or 10 times the picture
height, like it was intended to be.  But I sit a lot closer to my
workstation screen than that - 1-2 picture heights away.  And at that
distance, television is simply awful for "imaging", unless I specifically
want to see what my images will look like on television.

I suspect that what Rob really means is that, given you can only afford
1 megabyte of video RAM, you're better off arranging it as 640x480x24
than as 1024x768x8 if you're doing imaging - and he's right.  But
640x480x24 is, in fact, much better than television.

And if you can afford more video RAM, much higher resolution is useful,
provided you retain 24 bits for colour.  Extra pixels stop being useful
when you reach the point where a single pixel is about one arc minute
in size when seen from the viewer's eye.  For a CRT viewed from one
screen width away, that's about 3500 pixels horizontal resolution.  For
a viewing distance of two screen widths, the limit is about 1800.