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Re: changing presentation of links

From: Gregg Vanderheiden <gv@trace.wisc.edu>
Date: Fri, 22 Mar 2013 22:36:02 -0500
To: Jonathan Avila <jon.avila@ssbbartgroup.com>
Cc: Gregg Vanderheiden <gv@trace.wisc.edu>, Alastair Campbell <alastc@gmail.com>, W3C WAI ig <w3c-wai-ig@w3.org>
Message-id: <3B4811A4-5A06-4B0E-980B-8FD0E4FAAC2D@trace.wisc.edu>

On Mar 22, 2013, at 6:07 PM, Jonathan Avila <jon.avila@ssbbartgroup.com> wrote:

> [Greg wrote] .  It has to also be distinguishable before you point at it
> And by that do you mean there is a differentiation in color which makes it distinguishable? 

GV: Absolutely not.    Color cannot ever be the only difference.   We even have and SC on that.

But Red and Pink are the same color -- but have different lightness and contrast with each other.   So do any light and dark colors.

Color is HUE and should not be confused with 'lightness'.      If the links are substantially different lightness - it does not matter if they are the same or a different color than the surrounding text. 

> G183 seems to say you are good if there is a non-color differentiation on focus and on hover.  This certainly raises an interesting point  its not the use of any particular color that conveys meaning here but the difference in color. 

GV:  close but not color,     lightness.

> I would argue the best test for something like this is not grayscale but purely black and white because it would require evidence of other visual changes other than just color difference.  A grayscale check would potentially pass color differentiation but black and white would not.

GV:  yes this is close.   but be careful,  if you have colorblindness you don't see the same contrast as a black and white version.   But if you do look at the luminosity of the link and surrounding text (and you can use the contrast tools cited for the contrast provision to measure this)  -- and the contrast between the link text and the other text is enough -- that would be a good enough test according to the techniques  -- and that technique was deemed sufficient by the working group.

So - yes -- that it the right idea - but stick with color luminosity contrast rather than greyscale (since there are all sorts of different algorithms for making a color image greyscale -- so greyscale is indeterminate.

> Jonathan
> From: Gregg Vanderheiden [mailto:gv@trace.wisc.edu] 
> Sent: Friday, March 22, 2013 6:55 PM
> To: Alastair Campbell
> Cc: W3C WAI ig
> Subject: Re: changing presentation of links
> this issue was just raised in public comment.   If you don't see the reply there -- you will see the reply shortly.
> PS - G183 says more than that.  It has to also be distinguishable before you point at it -- the pointing only makes it more distinguishable.   
> so the failure and the G183 are not in conflict
> Gregg
> --------------------------------------------------------
> Gregg Vanderheiden Ph.D.
> Director Trace R&D Center
> Professor Industrial & Systems Engineering
> and Biomedical Engineering University of Wisconsin-Madison
> Technical Director - Cloud4all Project - http://Cloud4all.info
> Co-Director, Raising the Floor - International - http://Raisingthefloor.org
> and the Global Public Inclusive Infrastructure Project -  http://GPII.net
> On Mar 22, 2013, at 12:42 PM, Alastair Campbell <alastc@gmail.com> wrote:
> Hi everyone,
> Sorry to jump on an old thread, but I'm back in the accessibility
> universe now, and this came up today.
> Specifically on link colour and distinguishing links from general
> text, there's a conflict in the success & fail criteria for 1.4.1.
> The test from G183 [1] specifically says that changing the link on
> mouseover/focus to include an underline or other mechanism is ok,
> whereas F73 [2] says that is not sufficient.
> From the previous discussion, it sounds like G183 should be
> deprecated, as if we are talking about "people who cannot perceive
> color differences" then the contrast aspect is irrelevant.
> -Alastair
> 1] http://www.w3.org/TR/2012/NOTE-WCAG20-TECHS-20120103/G183
> 2] http://www.w3.org/TR/2012/NOTE-WCAG20-TECHS-20120103/F73
Received on Saturday, 23 March 2013 03:36:33 UTC

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