Path: utzoo!utgpu!watmath!onfcanim!dave
From: dave@onfcanim.UUCP (Dave Martindale)
Newsgroups: comp.graphics
Subject: Re: Re: ShowScan resolution
Message-ID: <17586@onfcanim.UUCP>
Date: 26 Feb 89 02:14:39 GMT
References: <14497@cup.portal.com> <17670009@hpfcdj.HP.COM>
Reply-To: dave@onfcanim.UUCP (Dave Martindale)
Organization: National Film Board / Office national du film, Montreal
Lines: 29

In article <17670009@hpfcdj.HP.COM> myers@hpfcdj.HP.COM (Bob Myers) writes:
>>re:  The Dataquest marketing study distributed at SIGGRAPH that described
>>     2K x 2K as optimal for humans
>
>"Optimal" does not necessarily mean "best"; certainly, you could see the
>difference between 2k x 2k and 4k x 4k displays, but is the 4k worth the
>extra money?

I'd describe "optimal" resolution for a single still image as "each pixel
subtends 1 minute of arc at the viewer's eye at the expected viewing
distance".  This is, more or less, the resolution limit of the eye.
More resolution than this is mostly wasted; less and it may not appear
razor-sharp.

The actual number of pixels in an image then depends on the viewing distance
and the field of view that you wish covered.  For example, an 8 x 10 inch
photograph viewed from 10 inches away covers a visual field of 53 x 44
degrees.  To cover this with 1-arc-minute pixels, you need 3438 x 2750 pixels.

Seems like more than 2K to me!  2048 is adequate for a 6-inch wide field
viewed from 10 inches, or a screen 30 feet wide viewed from 50 feet,
so 2K is probably fine for movies as seen from where most people in
the audience sit.  But it sure isn't good enough for IMAX.

Of course, if you are trying to do animation in real time on your hardware,
spatial resolution will have to be traded against screen update rates
(temporal resolution) to get the best-looking display for the intended
purpose for the money.  For a flight simulator, I'll take 256 pixels updated
60 times a second over 2k pixels updated once a second any day..