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Re: avoid "color contrast"

From: CAE-Vanderhe <gregg@raisingthefloor.org>
Date: Fri, 14 Mar 2014 01:30:25 -0500
Message-Id: <DB2FDA46-DF90-4C04-9597-6D7936C8EFD0@cae.wisc.edu>
To: Shawn Henry <shawn@w3.org>, public-comments-wcag20@w3.org, Eric Eggert <ee@w3.org>, "EO 'w3c-wai-eo@w3.org'" <w3c-wai-eo@w3.org>, Joshue O Connor <joshue.oconnor@cfit.ie>
Hi all,

   There are a number of reasons for not using the term Color Contrast.   Some of them are

For WCAG - the success criteria do not use “color contrast” but rather use “contrast”  or “contrast ratio" — and the definitions make it clear this is “luminosity contrast”.   Changing the requirement to any other type of contrast in the WCAG support documents, is changing the SC - which can not (should not ) be done. 

Luminosity Contrast is not the same as color contrast.   

Color Contrast is poorly defined - and there are several different definitions of what it is.   And none of them are what is specified in WCAG.  

Even the definition of color is obscure.   The same color (hue) with different darkness/lightness is considered the same color by some and different colors by others.       And   For those who say they are the same color (hue)   Red and Pink would have not color contrast but would have luminosity contrast and would be pass WCAG just fine.       So do  light gray and dark gray.      And contrasting colors may be the same for people with some types of color perception differences.   (again there is argument between people with different definitions of color  and of color contrast). 

WCAG used luminosity because it works for color deficiencies that cause different colors to become equal.  Color difference or contrast differs among users.     Even with WCAG luminosity - the value can be different visually than for people with full color vision . But the VALUES chosen in WCAG were chosen so that those with color perception differences would still have the same contrast or better than is recommended for people with no color deficiency.   

Most of the discussion above is why WCAG chose luminosity contrast ratio rather than another measure for contrast.   However once WCAG did choose this—  we should not be talking about other types of contrast in our documents — or using ‘color contrast’ as a synonym for luminosity contrast - and confusing people I would not think.  


Gregg


On Mar 13, 2014, at 3:12 AM, Joshue O Connor <joshue.oconnor@cfit.ie> wrote:

> Hi Shawn and all,
> 
>> Actually, *the wording used throughout those WCAG pages* is "contrast
>> ratio" and "luminance contrast". "Color contrast" is only used once in
>> the main text, and twice in the future techniques -- which EOWG assumed
>> was just an oversight.
> [...]
>> In conclusion, EOWG's comment to WCAG WG was to correct the couple of
>> places where "color contrast" seemed to be a mistake. :)
> 
> Ok, good stuff. Thanks for putting the issue on our radar and I look forward to working it out.
> 
> Josh
> 
>> Best,
>> ~Shawn
>> 
>> 
>> 
>> On 3/12/2014 3:55 PM, Joshue O Connor wrote:
>>> Hi Shawn,
>>> 
>>>> Please avoid the phrase "color contrast".
>>> 
>>> <chair hat off>
>>> I'm happy to discuss this but it could be a big ask - essentially you
>>> are technically right but there is a common vernacular amongst
>>> developers and the term 'colour contrast' is well established as 'it'
>>> - largely based on the language traditionally used by WCAG it's worth
>>> noting.
>>> 
>>> Also it's worth noting that even if light intensity is measured in
>>> lumens, and variations within RGB values represent (on screen) what we
>>> know as colour - as a 'cowpath' the term 'colour contrast' already has
>>> a lot of traction and common understanding so to switch now - or
>>> attempt to switch could create more dissonance than it is worth.
>>> 
>>> My 2 cents
>>> 
>>> Josh
>>> 
>>>> Some places we've found it:
>>>> *
>>>> http://www.w3.org/TR/UNDERSTANDING-WCAG20/visual-audio-contrast-contrast.html
>>>> 
>>>> 
>>>> *
>>>> http://www.w3.org/TR/2008/WD-UNDERSTANDING-WCAG20-20080430/visual-audio-contrast-contrast.html
>>>> 
>>>> 
>>>> 
>>>> Additionally, several pages include "color contrast" in the Resources
>>>> listings. We wonder if it would be worthwhile to add a note there, e.g.,
>>>> something along the lines of what we have at
>>>> <http://www.w3.org/WAI/eval/preliminary#contrast>: This accessibility
>>>> requirement is sometimes called sufficient "color contrast"; however,
>>>> that is incorrect — technically it's "luminance contrast"...
>>>> 
>>>> Thanks,
>>>> Shawn for EOWG
>>>> 
>>>> 
>>> 
>>> 
>>> 
>>> 
>> 
>> 
> 
> 
> 
Received on Friday, 14 March 2014 06:31:52 UTC

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