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RE: CLOSED: Issue #344 - take 2

From: Gregg Vanderheiden <gv@trace.wisc.edu>
Date: Tue, 13 Dec 2005 11:04:27 -0600
To: "'Gregg Vanderheiden'" <gv@trace.wisc.edu>, <w3c-wai-gl@w3.org>
Message-ID: <002c01c60007$46963ce0$8c17a8c0@NC6000BAK>

I just went to see if we could do a comparison - and I realized we can't
until we have the contrast algorithm that they propose to use with the L
statistic they list at the site.   It looks like this will be available in
January sometime.   

We'll can together a comparison at that time -- although the website refers
to a tool that has been developed that can be used to compare different
standards.   So perhaps they can use that tool to compare their algorithm
with our current algorithm at the 4 end conditions (black text, black
background, white text, white background) and in the middle somewhere - with
various different color anomalies for the two levels  (level 2 and level 3).
Basically something like the text/color swatches the group used in
evaluating the current rule before adopting it.   The group could then
compare the two approaches and see if it thinks their measure performs

I have to say in advance that the two are similar and we could develop
something that is lightness based if that is seen by the group as more
desirable.  You do have to introduce veiling glare which I don't see in
their lightness calculation but they may have in their contrast formula
(which they currently can't show us - til sometime in January).   

So let's sit back on this one and let them get past their conference. They
can then propose something to the group for us to consider. If they can
propose a specific alternate equation / criterion for our level 2 and level
3 guidelines there should still be time to consider them in January.   


 -- ------------------------------ 
Gregg C Vanderheiden Ph.D. 
Professor - Ind. Engr. & BioMed Engr.
Director - Trace R & D Center 
University of Wisconsin-Madison 

-----Original Message-----
From: w3c-wai-gl-request@w3.org [mailto:w3c-wai-gl-request@w3.org] On Behalf
Of Gregg Vanderheiden
Sent: Tuesday, December 13, 2005 10:29 AM
To: w3c-wai-gl@w3.org
Subject: RE: CLOSED: Issue #344


We looked at lightness (L) as part of our work.  We found that, depending on
the values you choose, you end up with comparable results to the algorithm
proposed.   The one we proposed however seemed to perform better at lower
black end.   I will forward comparisons - though it is a bit involved since
they didn't specify what the threshold values should be. 

The key to either approach would be to define the threshold values.  The
link you pointed to provides an equation but no values for the threshold.
Further, the tests to date have only been carried out on subjects without
vision impairments.   They are hypothesizing research with people who have
vision deficits but there has been none to date.   If we were to use this in
our guidelines (which is a possibility) we would need to have values for the
threshold within the next 3 months.   What values would they propose for
level 2 and 3?   What would it be based on?    Could they come up with them
within the next month?

 -- ------------------------------
Gregg C Vanderheiden Ph.D. 
Professor - Ind. Engr. & BioMed Engr.
Director - Trace R & D Center
University of Wisconsin-Madison 

-----Original Message-----
From: w3c-wai-gl-request@w3.org [mailto:w3c-wai-gl-request@w3.org] On Behalf
Of Roberto Scano (IWA/HWG)
Sent: Tuesday, December 13, 2005 10:05 AM
To: chris.ridpath@utoronto.ca; gv@trace.wisc.edu; w3c-wai-gl@w3.org
Subject: Re: CLOSED: Issue #344

Here is it:

----- Messaggio originale -----
    Da: "Chris Ridpath"<chris.ridpath@utoronto.ca>
    Inviato: 13/12/05 16.45.40
    A: "Roberto Scano (IWA/HWG)"<rscano@iwa-italy.org>,
    Oggetto: Re: CLOSED: Issue #344
    Thanks for the information. I agree with Gez that it looks sensible and 
    > Hi, there is also the italian algorithm proposed in the list.
    Roberto - Sorry I couldn't find it. Could you provide a link?

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Received on Tuesday, 13 December 2005 17:04:37 UTC

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