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Re: [TECH] Colour Difference Algorithm

From: Doyle Burnett <dburnett@sesa.org>
Date: Tue, 26 Aug 2003 10:28:36 -0800
To: Joe Clark <joeclark@joeclark.org>, W3C Web Content <w3c-wai-gl@w3.org>
Message-ID: <BB70E6D4.A82%dburnett@sesa.org>

To The Group -

Colourblindness is a complex issue and would likely not be easily summed-up
in even a scientific formula/algorithm.  I read with interest chapter 9 of
Joe's book and for the most part came away with what I already knew about my
own disability (if I dare call it a disability - more of a nuisance than
anything).  I am one of those white males who has red-green colourblindness
- one who went some 18 years without knowing I had colourblindness (not
until I received my physical exam notice to be drafted into the military).

Joe is right - persons with most types of color deficiencies actually see
colors.  Even individuals with red-green colourblindness see the colors red
and green (depending upon the background/foreground combinations of the
presented text, if we're talking text).  There are also issues of things
like Scoptopic Sensitivity Syndrome (Irlin Syndrome) or other light
refractive, light waveform issues.

As a group, we've talked about issues that center around colourblindness but
we do need to look at the fact that this is "just" one logical connection to
what I really see as a contrast issue (and, sorry to say, probably
brightness as well).  Colourblindness is something that rings in the mind of
those who hear the word.  We all know someone who is colourblind so that
makes color issues easy to pin on a particular group.

Like so much of what we are trying to do, the issue of visual perception
(for those of us with vision) or whatever we'd elect to call it are trying
to make things better for as many individuals as possible.  Accessibility is
different things to different individuals and we'll "probably" never reach
the 100% mark with regard to total accessibility but we should strive toward
that mark.  

So - I do not fully agree with either side of the coin on whatever the issue
is here but would appreciate positive direction with regard to steps that
can be taken to make the wording (whatever) such that web authors have a
better chance of "doing it" right.

Personally, contrast is a huge issue with me...agree or disagree, it's what
makes printed text possible for me to read - plain and simple.  So - a web
authors ability to KNOW what color combinations work, especially when
presenting text over a colored background is an important issue.  And, there
will likely be no way to accommodate everyone's individual needs from the
authoring end but that does not mean authors should not follow set standards
or guidelines.  

My two cents worth.


Doyle Burnett
Education and Training Specialist
Multiple Disabilities Program
Special Education Service Agency

On 8/26/03 8:23 AM, "Joe Clark" <joeclark@joeclark.org> wrote:

>> The current WCAG2 draft [1] checkpoint 1.6 is still missing an
>> algorithm for determining when "foreground content is easily
>> differentiable from background" regarding the use of colour.
> Because it can't be programmatically determined?
> Because, if we exclude colourblindness from consideration for a
> moment, the extent and variation of vision deficiencies are much too
> vast to be summed up in a nice formula?
>> The AERT document [2], technique 2.2.1 for the WCAG1 proposed an
>> algorithm that worked reasonably well but was not perfect. Some
>> colour combinations were passed, though many people would find them
>> unacceptable, and other colours were failed though many people would
>> find them acceptable.
> That's not a good sign, is it?
>> Note: I'm suggesting that the general term "colour difference"
>> includes, but is not limited to, a difference in brightness and a
>> difference in colour (separation along the colour spectrum). Other
>> factors such as saturation may also come into play.
> I believe the Working Group continues to:
> 1. misunderstand the nature of colour deficiency
> 2. mistakenly overgeneralize and project visual *impairment* onto
> issues of colour
> 3. ignore authoritative published research on colourblindness and
> accessibility
> When I see the Working Group getting past point 3 above, we can start
> talking about the fact that its emphasis on "contrast" (and now
> "brightness") is incorrect, is not going to help people with visual
> impairments read the Web better, and ignores the central issue:
> Colour. (And here's a talking point: Why isn't this an issue of user
> stylesheets?)
> The paragraph quoted above demonstrates this well, placing hue in the
> same category as brightness and saturation. It isn't.
>> Listed below are several sites dealing with colour on the web:
> And of course the WG continues to pretend that the weeks of research
> I put into Chapter 9 of my book, "Type and Colour," amounted to
> nothing.
> I spent days on end at the library. I talked to and E-mailed actual
> experts in colour deficiency and colour mapping. I had them vet my
> chapter before publication. (That chapter was proofed seven full
> times.) I sent the experts the published book and asked them to
> correct any errors that remained. No corrections were offered. I of
> course found some typing errors myself later on.
> <http://joeclark.org/book/errata/>
> The book's been out since October 2002 (with HTML version on the
> included CD-ROM), and that chapter was online in (not very
> accessible) PDF since, if memory serves, December. It's been online
> in HTML for months.
> <http://joeclark.org/book/sashay/TChapter09.html>
> <http://joeclark.org/book/sashay/serialization/Chapter09.html?GL>
> I can also forward the text to the list. In any event, use it to
> improve your guidelines.
> Free advice: Delete the current wording altogether until you do some
> more research.
Received on Tuesday, 26 August 2003 14:25:31 UTC

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