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Re: guideline 7.1 about screen flickering

From: <snsinfo@us.ibm.com>
Date: Fri, 27 Jul 2001 07:34:03 +0200
Message-Id: <200107270534.f6R5Y3N21808@zidane.inria.fr>
To: w3c-wai-ig@w3.org

Interesting, the 20Hz example [2] seems to be "going faster" than the 59hz
- - at least to the eyes and brains of a few folks around here.
I also checked my hardware and software display driver properties.  It's
currently set at 60Hz. which seems very close to 55 to me.  It appears that
the latest software that I have is still dependent on the physical hardware
capabilities of the display monitor.  The back of the physical display
monitor is rated at 50-60Hz and was built in 1997.  It's a nice 19 inch
model too.

The Access-Board technical information [1] only quotes another ICC/ANSI
standard, while the W3C reference [3] doesn't mention a source but sets the
guideline rate different at 4 to 59hz.

My TRACE reference [4] seems to explain it best to me, but how we ended up
with these different rates in the standards and guidelines is beyond me.
The detail behind the TRACE graph represents data from "photo-convulsive
response was elicited by a 2-second train of flashes".  These "flashes"
also affected the individuals when their eyes were closed.  How "flashes"
ended up being "screen flicker" is also beyond me.

[1] http://www.access-board.gov/sec508/guide/1194.22.htm#(j)
[2] http://ncam.wgbh.org/richmedia/flicker_demo.html
[3] http://www.w3.org/TR/WCAG10-CORE-TECHS/#flicker
[4] http://trace.wisc.edu/docs/consumer_product_guidelines/consumer.htm#o7

Regards,
Phill
Received on Friday, 27 July 2001 01:34:33 GMT

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