Edit comment LC-1414 for Accessibility Guidelines Working Group

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Comment LC-1414: Comment Shortname:; Commenter: David Keech <david.keech@bsi-global.com> on behalf of British Standards Instution, London, UK; Message-id:; Section of the document concerned:

or; Refinement of the section concerned:; Status:
assigned to; Type:; Resolution status:
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No response from Commenter yet Commenter approved disposition Commenter objected to disposition
Commenter's response (URI):; Comment:
12. The role of blinking and flashing content is confused -
http://www.w3.org/TR/WCAG20/complete.html#time-limits-blink and
http://www.w3.org/TR/UNDERSTANDING-WCAG20/#seizure-does-not-violate-terms

CLARIFICATION
________________________________________
From: David Keech [mailto:David.Keech@BSI-GLOBAL.COM]
Sent: Friday, July 21, 2006 7:46 AM
To: Gregg Vanderheiden
Subject: RE: comment #12 clarification
Gregg

Sorry for the delay in clarifying our comment.

Regarding our statement:

â€¢ â€œThe role of blinking and flashing content is hopelessly confused - http://www.w3.org/TR/WCAG20/complete.html#time-limits-blink and http://www.w3.org/TR/UNDERSTANDING-WCAG20/#seizure-does-not-violate-terms"

The distinction between blinking and flashing is very difficult to understand and is apparently drawn from human factors research into visual display devices such as television, where fairly precise measurement and control of flash rates is possible (we assume).

On the web we anticipate that the exact nature of the flash/blink behaviour will be affected by local conditions such as monitor refresh and hardware performance.

Furthermore, given that there are numerous ways to make an item Flash on the web, through the use of combinations of CSS and Javascript among other techniques, how can flash/blink rate be reliably tested?

If content cannot blink for more than three seconds (where blinking means "turn on and off between 0.5 and 3 times per second") it is presumably acceptable that content blinks for 0.49 times per second for 2.99 seconds....Is this sensible?

The most reliable method is to disallow blinking/flashing, any other suggestion is virtually impossible to work with in our view.

Please let me know if there is still any confusion.

Regards

David Keech
BSI
ICT/0070/06; Related issues: 878 IS PARENT
(space separated ids); WG Notes: [EDITORZ] {resonse written but awaiting final disposition on other 2.3 items} Sent note seeking clarification - and received response (see above) i wrote back ===== Hi David Thanks We will respond formally, but you are correct. Some of flicker or flash is a function of user agent. However, with fast computers, the flicker or flash is controlled by the content not the player. It is the content that must not cause flash. We will make that clearer in the WCAG materials, and also draw the distinction between blinking and flashing. Thanks again Gregg -- ------------------------------ Gregg C Vanderheiden Ph.D. ========================================================== original request for clarification: From: Gregg Vanderheiden [mailto:gv@trace.wisc.edu] Sent: Saturday, July 01, 2006 9:42 PM To: 'David Keech' Cc: 'public-comments-wcag20@w3.org' Subject: comment #12 clarification Hi David In your comments your #12 was 12. The role of blinking and flashing content is confused - http://www.w3.org/TR/WCAG20/complete.html#time-limits-blink and http://www.w3.org/TR/UNDERSTANDING-WCAG20/#seizure-does-not-violate-terms We do not understand what you mean. Blinking is a distraction problem. Content that blinks can cause problems for some users. If it stops within 3 seconds â€“ it only provides a delay not a barrier. And the blinking can be a useful tool for all users including people with cognitive disabilities or low vision to draw their attention to something important. Blinking at slower than 4 per second is not as seizure problem. Flashing on the otherhand refers to flashes that are more than 3 per second. This is a seizure problem even for a second. To keep these separate we refer to one as blinking and one as flashing. (At least we tried to) From your comment it sounds like you found a place where one of them is crosslinked with a technique for the other. Or perhaps you found something else. If you could clarify where you think we have these confused or used the wrong term it would be most helpful. Or does this answer your question? Thank you. Gregg Co-chair Discussed in the 04 January 2007 telecon: resolution: Accept LC 1414 as amended http://www.w3.org/WAI/GL/2007/01/04-wai-wcag-minutes.html Accept DONE Add to the definition of BLINK Note: The slower blink is in contrast with flashing, which refers to rapid changes in brightness which can cause seizures. See [general flash threshold] and [red flash threshold]. DONE Add the following paragraph to INTENT of HTM 2.3 between paragraph 2 and 3. "Flashing can be caused by the display, the computer rendering the image or by the content being rendered. The author has no control of the first two. They can be addressed by the design and speed of the display and computer. The intent of this criterion is to ensure that flicker that violates the flash thresholds is not caused by the content itself. For example, the content could contain a video clip or animated image of a series of strobe flashes or close-ups of rapid fire explosions." XML updated 19 January 2006.; Resolution: We have made the following changes to clarify the differences between blink and flash: The following note was added to the definition of "blink": Note: The slower blink is in contrast with flashing, which refers to rapid changes in brightness which can cause seizures. See general flash and red flash thresholds. The following paragraph was added to the intent section of How to Meet Success Criterion 2.3.1: "Flashing can be caused by the display, the computer rendering the image or by the content being rendered. The author has no control of the first two. They can be addressed by the design and speed of the display and computer. The intent of this criterion is to ensure that flicker that violates the flash thresholds is not caused by the content itself. For example, the content could contain a video clip or animated image of a series of strobe flashes or close-ups of rapid fire explosions."; (Please make sure the resolution is adapted for public consumption)