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RE: guideline 7.1 about screen flickering

From: Charles McCathieNevile <charles@w3.org>
Date: Tue, 24 Jul 2001 14:42:46 -0400 (EDT)
To: "Fitzgerald, Jimmie" <Jimmie.Fitzgerald@jbosc.ksc.nasa.gov>
cc: "'Terrie King'" <tking@ucp.org>, <w3c-wai-ig@w3.org>
Message-ID: <Pine.LNX.4.30.0107241432550.4232-100000@tux.w3.org>
I am not so sure. The thing moves in my viewer at the sort of rate that is
potentially a problem (between 5 and 50 hertz, roughly) for people with
photosensitive epilepsy, and is distracting for people with concentration
difficulties. I think if it is going to be fine it will be so on the basis
that it is easy to stop animations in modern browsers, and I am not sure if
the WCAG group has actually worked out whether or not that is the case in the
real world to the extent that they are now happy about it. I will follow up
in that group - the archive is public so you can read along from
and people are able to subscribe to that group if they want to join the


Charles McCN

On Tue, 24 Jul 2001, Fitzgerald, Jimmie wrote:

  Looks fine to me.  It isn't flickering at all.  What 'they' call screen
  flicker is more in the lines of image changeouts and color changing.  They
  really need to change their wording to 'element flicker' or something.  By
  calling it screen flicker, I think monitor refresh rates.  And that is
  something we as developers cannot control.

  Your .gif is good to go.

  Jim Fitzgerald

  -----Original Message-----
  From: Terrie King [mailto:tking@ucp.org]
  Sent: Tuesday, July 24, 2001 10:45 AM
  To: w3c-wai-ig@w3.org
  Subject: guideline 7.1 about screen flickering

  Okay, experts!  I have been asked to put another agency's animated gif on my
  Web site.  I am hesitant to  use it because of guideline 7.1--"Until user
  agents allow users to control flickering, avoid causing the screen to
  flicker."  Here's the link to the checklist item:

  How can I determine if the gif in question is within the guidelines?  (gif
  attached)  If it is not, I guess I can ask for a non-animated gif.


  Terrie L. King
  Internet Marketing Manager

  UCP National
  1660 L Street, NW, Suite 700
  Washington, DC  20036
  Ph: 800-872-5827
  Fax: 202-776-0414
  Web site:  http://www.ucp.org

Charles McCathieNevile    http://www.w3.org/People/Charles  phone: +61 409 134 136
W3C Web Accessibility Initiative     http://www.w3.org/WAI    fax: +1 617 258 5999
Location: 21 Mitchell street FOOTSCRAY Vic 3011, Australia
(or W3C INRIA, Route des Lucioles, BP 93, 06902 Sophia Antipolis Cedex, France)
Received on Tuesday, 24 July 2001 14:43:08 UTC

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