Thread Subject: Re: Flashing provisions

From: Hoffman, Allen
Date: Mon, Apr 09 2007 8:25 AM

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I am not following all of this.
I'll go read the WCAG first.

I still don't understand how the field of vision can be determined by
the developer and be accurate for the variety of screen
sizes/resolutions and visual abilities of the end-users.



Allen hoffman -- 202-447-0303

-----Original Message-----
From: = EMAIL ADDRESS REMOVED =
[mailto: = EMAIL ADDRESS REMOVED = ] On Behalf Of Gregg
Vanderheiden
Sent: Monday, April 09, 2007 10:12 AM
To: 'TEITAC Web/Software Subcommittee'
Cc: 'Peterson, Bill'
Subject: Re: [teitac-websoftware] Flashing provisions

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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