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Re: guideline 7.1 about screen flickering (fwd)

From: Anne Pemberton <apembert@erols.com>
Date: Thu, 26 Jul 2001 11:33:24 -0400
Message-Id: <>
To: "gregory j. rosmaita" <oedipus@hicom.net>, <w3c-wai-gl@w3.org>
Cc: <andrew_kirkpatrick@wgbh.org>

         Thanks for these links. They are VERY illustrative. I am not 
photo-sensitive, so I stayed and stared at the demos, all of them together, 
and each of them individually, set at full screen on a large monitor. I do 
not usually use the web at full screen unless I can't see enough of a page 
... (my working style) ... At first I thought there was no effect, perhaps 
because the contrast between blue and white wasn't enough, or because a 
relatively small part of the screen was actually flashing. After about five 
minutes, I clicked off, and within a few minutes suffered a visual 
distortion and slight mental disorientation that is just now fading some 30 
minutes after I got off the site.

         So, I'd say the guy made a good demonstration, and his warning for 
those who are sensitive to such effects to not experiment with the site, is 

         I think we should include the parameters for the cautionary range 
of flash in the sufficiency criteria somewhere in the guidelines.

         One thought that comes to mind. Do we need to look at the 
cumulative effect of flashing on a screenful of animations which may each 
individually be OK? Is it possible to measure that?


At 11:07 PM 7/26/01 -0400, gregory j. rosmaita wrote:
>[speaking of implementing, kudos to andrew kirkpatrick of WGBH/NCAM who, in
>response to this thread on w3c-wai-ig slapped together a very illustrative
>resource, which is described at:
>and which can be accessed at:
>as far as whether or not we can state, either in good faith or good
>conscience, that the "until user agent" clause of 7.1 is obsolete, from the
Received on Friday, 27 July 2001 11:38:48 UTC

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