RE: Color contrast

As I recall there were three types of color sensors, the red yellow and
Blue.

Any or all off these can be low impaired or missing entirely.

For people who are completely color blind (no color vision at all) it is
only the gray scale that counts, so a red on black is completely invisible
 I actually wrote to them a year ago or so, and got some conformation on
this)

If someone has no blue vision, then having a high contrast just biased on
the blue scale is not sufficient. Of course the same is true for the other
cones.
So you need sufficient contrast in each of the fundamental colors, to
guarantee contrast for all color disabilities (not just the common ones).


All the best

Lisa Seeman

-----Original Message-----
From: w3c-wai-gl-request@w3.org [mailto:w3c-wai-gl-request@w3.org]On
Behalf Of Gregg Vanderheiden
Sent: Wednesday, June 05, 2002 3:25 AM
To: 'Loretta Guarino Reid'; w3c-wai-gl@w3.org
Subject: RE: Color contrast



Interesting.  But how does that control for color blindness?

The problem is contrast, not color difference.   Are they the same?

Thanks

Gregg

------------------------------------
Gregg Vanderheiden Ph.D.
Ind Engr - Biomed - Trace,  Univ of Wis
gv@trace.wisc.edu




> -----Original Message-----
> From: w3c-wai-gl-request@w3.org [mailto:w3c-wai-gl-request@w3.org] On
Behalf
> Of Loretta Guarino Reid
> Sent: Thursday, May 30, 2002 7:27 PM
> To: w3c-wai-gl@w3.org
> Subject: Color contrast
>
>
> I checked with Lars Borg, one of Adobe's color scientists, about the
best way
> to evaluate the contrast between two RGB colors. Here is his advice:
>
> Convert each color to Lab, then calculate the length of the difference
> vector in Lab (also known as deltaE). The distance is a fairly
> consistent measure of color difference. Contrasting colors may need a
> deltaE of 40 or more. (This needs to be verified.)

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Received on Wednesday, 5 June 2002 02:45:49 UTC