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RE: Tech G19

From: Roberto Scano \(IWA/HWG\) <r.scano@webprofession.com>
Date: Thu, 19 Mar 2009 14:59:46 +0100
To: "'Gregg Vanderheiden'" <gv@trace.wisc.edu>
Cc: "'WCAG'" <w3c-wai-gl@w3.org>
Message-ID: <49c24fd5.06a1660a.69f7.ffffc5be@mx.google.com>
Than u Gregg!

-----Original Message-----
From: Gregg Vanderheiden [mailto:gv@trace.wisc.edu] 
Sent: Thursday, March 19, 2009 2:54 PM
To: Roberto Scano (IWA/HWG)
Cc: 'WCAG'
Subject: Re: Tech G19

Hi Roberto

the comment is correct but poorly worded.  We will need to fix that

  at level A you need to pass the General and Red Flash Thresholds.

these thresholds give you the option.

EITHER
- don't flash more than 3.5 times in any one second period
OR
- the flash must be smaller or dimmer than a threshold.

At level AAA it says that you must no flash more than 3.5 times in any  
one second period.  Period.




Technique G19 says - just don't flash less than 3.5 time in any one  
second period.      This will indeed pass both the Level A and the  
Level AAA Success criteria.  But it is more strict than Level A  
requires (since level A does allow more than 3.5 flashes if they are  
small or low contrast enough.

Also the word "failure" is confusing since it is referring to things  
that would fail the thresholds - but it makes you think it is talking  
about the "common failures"

So we should change the note to read something like


Note 1: This technique is stricter than the Level A Success Criteria
since the Level A success criteria 2.3.1 allows more than 3.5 flashes
in one second if they are small or low contrast enough.
But having no more than 3.5 flashes within any one second period would  
meet
the Level A success criteria  (and the Level AAA success criteria  
2.3.2 as well).
It is also much easier to test. Most content does not flash at all and
even content that blinks does not blink this fast except on rare  
occasions.
Therefore, in order to avoid having to carry out the more complex  
testing
specified by the Level A Success Criteria 2.3.1, one could follow this  
technique
and ensure that content only flashes one, two, or at most three times  
in any 1-second
period.


Thanks for catching this.


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







On Mar 19, 2009, at 8:04 AM, Roberto Scano (IWA/HWG) wrote:

> Hi all, i think there is a mistake here:
>
>
> http://www.w3.org/TR/2008/NOTE-WCAG20-TECHS-20081211/G19
>
>
> Note 1 said:
>
> ---
> Note 1: This technique is stricter than the Level 1 Success Criteria  
> but is
> easier to test and can be used to meet the Level 1 Success Criteria  
> because
> all failure thresholds in the Level 1 Success Criteria involve  
> flashing 3.5
> flashes or more within one second. Most content does not flash at  
> all and
> even content that blinks does not blink this fast except on rare  
> occasions.
> Therefore, in order to avoid having to carry out the more complex  
> testing
> specified by the Success Criteria, one could follow this technique  
> to ensure
> that content only flashes one, two, or at most three times in any 1- 
> second
> period.
> ---
>
> But this Is a level 1 success criteria and i don't find any failure  
> for the
> cited 3.5 flashes:
>
> http://www.w3.org/TR/UNDERSTANDING-WCAG20/seizure-does-not- 
> violate.html
>
>
>
> ---
> Roberto Scano (rscano@webprofession.com)
> International Webmasters Association / HTML Writers Guild
>
>
>
>
>
Received on Thursday, 19 March 2009 14:00:32 GMT

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