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RE: changing presentation of links

From: Jonathan Avila <jon.avila@ssbbartgroup.com>
Date: Mon, 25 Mar 2013 16:40:14 -0400
Message-ID: <ae8e914cf1dde51ce0205c26724b058d@mail.gmail.com>
To: Gregg Vanderheiden <gv@trace.wisc.edu>
Cc: Alastair Campbell <alastc@gmail.com>, W3C WAI ig <w3c-wai-ig@w3.org>
*[Greg Wrote]*

Ř  *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. *



My mistake, I get so use to the misnomer “Color contrast” that I said that
rather than luminosity.    I hope that the workgroup can at least update
the term in the non-normative documents to be correct.



Ř  *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.  *

I was referring (but not very clearly) to plain black on white –
monochrome.  I think this is something Chaals referred to.  That would be
the best definitive test – but as you mention goes beyond the intent of the
SC as defined by the working group.



Jonathan





*From:* Gregg Vanderheiden [mailto:gv@trace.wisc.edu]
*Sent:* Friday, March 22, 2013 11:36 PM
*To:* Jonathan Avila
*Cc:* Gregg Vanderheiden; Alastair Campbell; W3C WAI ig
*Subject:* Re: changing presentation of links







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 – it’s 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 Monday, 25 March 2013 21:02:56 GMT

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