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Re: BODY Colors

From: Leonard R. Kasday <kasday@acm.org>
Date: Tue, 30 Mar 1999 12:02:29 -0500
Message-Id: <>
To: "Chris Ridpath" <chris.ridpath@utoronto.ca>, "WAI ER IG List" <w3c-wai-er-ig@w3.org>

>The problem now is how do we quantify the colors. On your computer, the
>colors are represented by 3 values (red, green and blue) and the values
>range from 0 to 255. So what represents a poor visibility red? What values
>make up a 'dark' background?

The values are mapped to screen intensity in a non linear way, roughly. a
power function.  v^gamma.  To make matters more complicated, gamma is
different for Mac's, PC's, and some unix machines like SGI.

In addition, the allowable contrast difference depends on the size of the

I looked at this a while back and didn't find satisfactory quantitative
data, even for people with "normal" vision.  

We have the makings here of a good research project.  At least an update on
the literature search I did.  Possibly some experiments.

If someone wants to do a bit of research I'll be glad to dig up my old notes.

Perhaps there are folks in the psychology dept up there who would like to
look into this... viz. the folks in visual perception.


Leonard R. Kasday, Ph.D.
Universal Design Engineer, Institute on Disabilities/UAP, and
Adjunct Professor, Electrical Engineering
Temple University

Ritter Hall Annex, Room 423, Philadelphia, PA 19122
(215} 204-2247 (voice)
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Received on Tuesday, 30 March 1999 12:26:11 UTC

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