- From: doyle saylor <doylesaylor@mac.com>
- Date: Thu, 13 Mar 2014 08:17:12 -0700
- To: Andrew Kirkpatrick <akirkpat@adobe.com>
- Cc: Joshue O Connor <joshue.oconnor@cfit.ie>, Shawn Henry <shawn@w3.org>, Eric Eggert <ee@w3.org>, "EOWG (E-mail)" <w3c-wai-eo@w3.org>
Hello Andrew, For readability the lightness or darkness of a color to it's background comes first. In regard to color blindness one can't be sure a member of the public discerns the same color as the developer, but lightness or darkness is visible. Color contrast refers to how the eye will produce vivid visual after effects due to the stimulation and saturation of one color on the retina. The after effect colors are the so-called contrasting colors. Color seeing itself is not closely aligned to shape discernment. This shows up in the famous equiluminescent paintings of Monet of the Chartres cathedral in which the shape of the cathedral is hard to discern despite using contrasting colors to define shadow shapes. Using contrasting colors can make it harder to see the shape of letters if one is not sensitive to lightness and darkness as the primary aspect of seeing shape. Luminescence is just a technical term referring to the measure of light off a surface, but simply using the descriptors; lightness and darkness, suffices to clarify what is meant. Doyle Saylor Sent from my iPad > On Mar 13, 2014, at 7:49 AM, Andrew Kirkpatrick <akirkpat@adobe.com> wrote: > > So what is the basis for how different colors contrast? > > For readability contrast, WCAG doesn't talk about that directly at all - it bases the readability of the content on the contrast algorithm, which is calculated by evaluating the luminosity values of the text and background colors. So they seem to be the same thing in WCAG, don't they? > > AWK > > -----Original Message----- > From: doyle saylor [mailto:doylesaylor@mac.com] > Sent: Thursday, March 13, 2014 10:12 AM > To: Andrew Kirkpatrick > Cc: Joshue O Connor; Shawn Henry; Eric Eggert; EOWG (E-mail) > Subject: Re: avoid "color contrast" > > Hi All, > Color contrasts refers explicitly to how different colors contrast. That contrast which is very visible comparing red to blue for example does not refer to lightness or darkness. Whereas readability contrast really rests upon discerning letter shapes against a background. Color contrasts introduces an ambiguity to discerning text that makes the job of a web developer harder. > Doyle Saylor > > Sent from my iPad > >> On Mar 13, 2014, at 6:30 AM, Andrew Kirkpatrick <akirkpat@adobe.com> wrote: >> >> I think that we need to discuss this more. I do note that the phrase "color contrast" isn't in the WCAG spec, but does appear in 16 places in the techniques (all in link text) and 15 times in Understanding. >> >> I'm reluctant to go along with "luminance contrast" as I agree with the document at http://www.w3.org/WAI/eval/preliminary#contrast which says that this sounds jargony. I'm also not sure that I would say that "color contrast" is incorrect, although this same page says that. >> >> Can someone explain why it is incorrect? I can agree that it is probably less precise than "luminance contrast" but as luminance is a property of color it seems that when we say color contrast that we are really saying "contrast between the luminance values for two colors". >> >> There's a bunch of links that we have in understanding where the authors have chosen to use "color contrast". Much of the advice on color in WCAG 2.0 actually came from Lighthouse for the Blind researchers - if this terminology doesn't bother them, should it bother us? >> http://www.lighthouse.org/accessibility/design/accessible-print-design >> /effective-color-contrast >> >> I guess I'm pushing back on the ideas that we shouldn't use "color contrast" and should use "luminance contrast". We have a defined term that is "contrast ratio" but it refers to color luminance, so I'm really not clear on the harm of saying "color contrast ratio". I feel that when we say "color contrast" people understand that there is some sort of color difference that needs to be provided, and if we say "luminance contrast" people will say "huh?". >> >> So, why is "color contrast" incorrect? >> >> Thanks, >> AWK >> >> -----Original Message----- >> From: Joshue O Connor [mailto:joshue.oconnor@cfit.ie] >> Sent: Thursday, March 13, 2014 4:13 AM >> To: Shawn Henry >> Cc: public-comments-wcag20@w3.org; Eric Eggert; EOWG (E-mail) >> Subject: Re: avoid "color contrast" >> >> 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-con >>>>> t >>>>> rast.html >>>>> >>>>> >>>>> * >>>>> http://www.w3.org/TR/2008/WD-UNDERSTANDING-WCAG20-20080430/visual-a >>>>> u >>>>> dio-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 12:56:50 UTC