Thread Subject: Re: Flashing provisions

From: Gregg Vanderheiden
Date: Mon, Apr 09 2007 8:30 AM

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Yes.
That is why there is a value given for web content. The same value can be
used for any software that is played on unknown screens etc. If the screen
size and resolution and or viewing distance is known to be different then
that can be used instead.

It is worded as 'web content' because it was for WCAG. We can adjust.

If you want to avoid all the calculation parts you can simply avoid having
any flashing more than 3 in any one second period and you pass
automatically.

The other provisions allow you to have flashing in the span if you know it
will be less than 25% of 10 degrees of view. IN that way you can allow
flickering 'disk busy' lights or IP traffic LEDs etc. (though fully
saturated red would be good to avoid)


Gregg
-- ------------------------------
Gregg C Vanderheiden Ph.D.



> -----Original Message-----
> From: = EMAIL ADDRESS REMOVED =
> [mailto: = EMAIL ADDRESS REMOVED = ] On Behalf
> Of Hoffman, Allen
> Sent: Monday, April 09, 2007 9:02 AM
> To: TEITAC Web/Software Subcommittee
> Cc: Peterson, Bill
> Subject: Re: [teitac-websoftware] Flashing provisions
>
> How is the visual field determinable? Wouldn't that depend
> upon the viewer, distance from screen, size of screen, and
> many factors beyond the developers control?
>
>
>
> Allen Hoffman -- 202-447-0303
>
> -----Original Message-----
> From: = EMAIL ADDRESS REMOVED =
> [mailto: = EMAIL ADDRESS REMOVED = ] On Behalf
> Of Andi Snow-Weaver
> Sent: Monday, April 09, 2007 9:48 AM
> To: = EMAIL ADDRESS REMOVED =
> Subject: [teitac-websoftware] Flashing provisions
>
>
> 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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