- From: Phill Jenkins <pjenkins@us.ibm.com>
- Date: Tue, 27 Oct 2009 22:42:10 -0500
- To: w3c-wai-ig@w3.org
- Cc: public-comments-wcag20@w3.org
- Message-ID: <OFFFC7AFE6.86A4D01A-ON8625765D.000EB704-8625765D.0014575E@us.ibm.com>
Is the duration of the flashing or flickering (i.e., more than one second
of time) a factor in determining accessibility compliance to WCAG 2.0
See Success Criteria 2.3.1 http://www.w3.org/TR/WCAG20/#seizure
"... do not contain anything that flashes more than three times in
any one second period..."
In my special case example, there is a slightly less than 1 second
duration of 3 flashes in an Adobe Flash image at the top of a draft
Shanghai EXPO 2010 page.
WARNING - currently it flashes 3 times for slightly less than one second,
then repeats several seconds later.
see http://fr.expo2010.cn/indextest.htm
Assuming the developer adds a capability to stop the repeating Adobe Flash
movie, is it still a problem because it flashes 3 times, regardless of the
duration (e.g., 1 second, 10 seconds, etc.)? Or does it need to flash
more that 3 times a second of time for more that 1 second of duration?
The "Understanding Guidelines 2.3" further mentions: "likely to cause
seizure when viewed even for a second or two."
see http://www.w3.org/TR/UNDERSTANDING-WCAG20/seizure.html
metrics to consider: Frequency, Duration, and Size (the text only really
address frequency and size, not duration)
frequency: (or interval) more than 3 flashes per second of
time? (3 to 50 Hz)
duration: more than one second duration of time? if it
flashes more than 3, but for less than 1 second, is it a problem?
size: 341 x 256 pixel block or larger - see
http://www.w3.org/TR/WCAG20/#general-thresholddef
Since my example only flashes 3 times and not more than 3, and it soon may
change to not repeat - Guidelines 2.3 says "more than three", then I think
I do not have a problem, but I'm not sure - hence the question to the
list. Your informed opinions welcomed.
I also believe the text and explanation can be simplified. For example:
1. by addressing the three different metrics; frequency, duration, and
size.
2. by addressing the lower and upper limits of each. For example, if the
frequency is 40 times in a second, but only lasts 1 second or less,
regardless of size it may be hardly noticeable and not be a problem.
3. add some more common passing and failing examples. The two existing
ones are good.
Regards,
Phill Jenkins,
Received on Wednesday, 28 October 2009 03:42:46 UTC