Re: Your comments on WCAG 2.0 Public Working Draft of May, 2007

We have added mention of this issue to the Understanding documents,
and added an advisory technique for graphs and charts.

Contrast with the background is covered by the definition of contrast
ratio, which mentions specifically that the ratio is between the
foreground and the background.

Regards,

Loretta Guarino Reid, WCAG WG Co-Chair
Gregg Vanderheiden, WCAG WG Co-Chair
Michael Cooper, WCAG WG Staff Contact

On behalf of the WCAG Working Group

> ----------------------------------------------------------
> Comment 2: 1.4.3 and 1.4.5 missing "background" ? only text ?
> Source: http://lists.w3.org/Archives/Public/public-comments-wcag20/2007Jul/0032.html
> (Issue ID: 2318)
> ----------------------------
> Original Comment:
> ----------------------------
>
> Current wording: "Text (and images of text) have a contrast ratio of
> at least..." It seems you need to say that the text has a contract
> ratio with it's background, e.g., previous wording "Text or diagrams,
> and their background, have a luminosity contrast ratio of at least
> 5:1"
>
> Also, does this really only cover text? Are other things -- such as
> data in a graph -- covered elsewhere?
>
> ---------------------------------------------
> Response from Working Group:
> ---------------------------------------------
>
> You will find the word 'backgound' in the definition of "contrast
> ratio".  It is commonly understood that requiring text to have
> contrast means contrast with what is immediately behind it. We removed
> the phrase 'and their background', since this is often a relative
> concept in technologies like HTML/CSS that can scroll or reflow and
> have partial opacity. In general what is 'background' is not knowable
> until the final rendering, and the original clause implied a level of
> fixity which was not appropriate. It is therefore better handled in
> the definitions where it talks about foreground and background and it
> is clearer.
>
> We are only applying this to text because when we tried applying it to
> other things like graphs and charts we ended up with numerous
> exceptions and problems.      In the end we decided that the most
> severe problem was reading running text when the contrast is very low.
>
> Shawn: I am uncomfortable with not having contrast for things such as data in a graph or chart included in the guidelines. However, I don't want to hold up moving WCAG 2.0 forward over it. Therefore, I am satisfied with the response. Would you consider addressing this in Understanding; that is, clarifying somewhere that there should be sufficient colour contrast on things like graphs and charts, even though it is not a requirement.
>
>   Also, data in a graph would need to be described in a long
> description - and can be viewed under magnification.
>
> Shawn: This doesn't help for many people who need significant colour contrast. It is common for people with diminishing vision due to ageing to need good colour contrast, and not have a user agent or AT that provides access to the long description.
>

Received on Wednesday, 12 December 2007 00:10:18 UTC