Thread Subject: Rewrite of 21(j)

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From: Andrew LaHart
Date: Mon, Nov 13 2006 8:10 AM

Hello,
Thank you Luke for the ISO language. Below is a suggested rewording of
21(j). In the Nov 6 subcommittee meeting, the popular comment was that
21(j) is not currently testable, and that it
should include a minimum contrast ratio. Either of the rewordings below
should address both of these comments.

[Proposed new language:]
OPTION 1 - 1194.21(j) When a product permits a user to adjust color and
contrast settings, at least one of the color selections provided shall
produce a minimum luminosity contrast ratio of 5:1.

OPTION 2 - 1194.21(j) When a product permits a user to adjust color and
contrast settings, at least one color selection capable of producing a
minimum luminosity contrast ratio of 5:1 shall be provided.

I prefer Option 2. This approach will require a definition luminosity
contrast ratio. We could re-use the definition that is used in WCAG 2.0
(http://www.w3.org/TR/WCAG20/appendixA.html#luminosity-contrastdef)

Luke also mentioned he likes the ISO language that requires an acceptable
default contrast. I agree, and I recommend we make a minimum ratio, say
3:1, for that one as well, so that it is testable. We could include a NEW
paragraph that says:

[Proposed new paragraph]
"Default combinations of foreground and background colours (hue and
luminance) should produce a minimum luminosity contrast ratio of 3:1."

Andrew LaHart
IBM Human Ability and Accessibility Center
703-831-4237 (direct)
http://www.ibm.com/able

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