Thread Subject: Flashing provisions
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From: Andi Snow-Weaver
Date: Mon, Apr 09 2007 7:55 AM
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When we discussed the flashing provision, we talked about harmonization
with WCAG 2.0 but determined that the WCAG 2.0 wording was too confusing
and not mature enough at the time. The WCAG working group has recently
settled on the following wording which is much simpler than what they had
before:
No more than 3 flashes above thresholds
No part of the product flashes more that three times in any one
second period unless
a) the flashing is greater than 50 hz or
b) the combined area of flashing occurring concurrently
and contiguously occupies less than one quarter of any 10 degrees of visual
field
c) the flashing is not fully saturated red and the
change in brightness is less than 10 percent of full scale brightness.
This is being proposed in the general subcommittee. Are there any issues
with replacing 21 (k) and 22 (j) with similar wording?
21 (k):
Current: Software shall not use flashing or blinking text, objects, or
other elements having a flash or blink frequency greater than 2 Hz and
lower than 55 Hz.
Proposed: Software shall not use flashing or blinking text, objects, or
other elements having a flash or blink frequency of more than three times
in any one second period unless:
a) the flashing is greater than 50 hz or
b) the combined area of flashing occurring concurrently and
contiguously occupies less than one quarter of any 10 degrees of visual
field
c) the flashing is not fully saturated red and the change in
brightness is less than 10 percent of full scale brightness.
22 (j):
Current: Pages shall be designed to avoid causing the screen to flicker
with a frequency greater than 2 Hz and lower than 55 Hz.
Proposed: Pages shall be designed to avoid causing the screen to flicker
more than three times in any one second period unless:.
a) the flashing is greater than 50 hz or
b) the combined area of flashing occurring concurrently and
contiguously occupies less than one quarter of any 10 degrees of visual
field
c) the flashing is not fully saturated red and the change in
brightness is less than 10 percent of full scale brightness.
Note that 55 Hz was apparently a typo in 508 and should have been 50 Hz.
Andi
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