Re: 4.4.1 and 4.4.2

Thanks, Simon and Kim!

I had three questions/suggestions.


First, I certainly agree that 4.4.1 should say that it's OK to flash if it's less than three times in a second to be consistent with WCAG and other guidelines. However, while your draft says the same thing as WCAG2's 2.3.1, it uses different structure and wording. If there isn't a good reason to diverge, I'd recommend using their wording with only the minimum changes necessary to adapt it from content to UI:

"4.4.1 Three Flashes or Below Threshold: The user interface does not contain anything that flashes more than three times in any one second period, or the flash is below the general flash and red flash thresholds. (Level A)"

(FYI for comparison, ISO 9241-171 uses a much more general guideline, putting the specifics into secondary documents and Notes:

"10.1.1 Avoid seizure-inducing flash rates
Software shall avoid flashing that could induce seizures in individuals with photosensitive seizure disorders.
NOTE 1	Standards in this area are currently undergoing revision and adaptation to apply to new displays.
NOTE 2	Less than three flashes in any 1 s period meets all current standards.")



Second, I'm not clear on whether you're suggesting merging 4.4.2 into 4.4.1, or just combining their Understanding/Examples. Since 4.4.1 is only Level AAA, deleting it wouldn't be tragic, but I'd keep it to stay in sync with them. By including both, 4.4.1 tells developers "If you must flash more than three times per second, keep it to low areas or luminance differences", while 4.4.2 adds "But it's even better if you just don't flash more than three times per second".



Third, the explanatory paragraph is good but I thought it could (a) be slimmed down without losing anything, (b) more clearly identify the two behaviors with the two terms, General Flash and Red Flash, (c) could more clearly differentiate photosensitive seizure disorder from the more common form of photosensitivity. Perhaps there's something in this version you could use:

"The intent of this Success Criterion is to guard against inducing seizures in individuals with photosensitive seizure disorders. Potentially harmful flashes occurs when there is a pair of significantly opposing changes in luminance (general flashing), or a transition to or from a saturated red occurs irrespective of luminance (red flashing)."

	Thanks,	
	Greg


-------- Original Message  --------
Subject: 4.4.1 and 4.4.2
From: Simon Harper <simon.harper@manchester.ac.uk>
To: UAWG list <w3c-wai-ua@w3.org>
Date: Thu, 3 Dec 2009 09:39:44 +0000

Again, Kim and I had this action, but looking at this I think we should 
amalgamate these two into:

4.4.1 The user interface never violates the general flash or red flash 
thresholds, or flashes more than three times in any one second period 
(Level A)

Intent of Success Criterion 4.4.1:
The intent of this Success Criterion is to guard against inducing 
seizures due to photosensitivity, which can occur when there is general 
flashing, or red flash. A potentially harmful flash occurs when there is 
a pair of significantly opposing changes in luminance, or irrespective 
of luminance, a transition to or from a saturated red occurs.

Examples of Success Criterion 4.4.1:
A single, double, or triple flash -- as long as it does not include 
changes to or from a saturated red -- may be used to attract a user's 
attention, or as part of an interface animation.

Related Resources for Success Criterion 4.4.1:
ITC Guidance Note for Licensees on Flashing Images and Regular Patterns 
in Television: 
http://www.ofcom.org.uk/tv/ifi/guidance/legacy/vrs_code_notes/flsh_imgs/gn_flash.pdf 



Best
Kim and Si.

Received on Thursday, 3 December 2009 17:52:39 UTC