- From: Simon Harper <simon.harper@manchester.ac.uk>
- Date: Thu, 14 May 2009 19:35:19 +0100
- To: UAWG list <w3c-wai-ua@w3.org>
So this is what I've dug up on this... A potentially harmful flash occurs when there is a pair of opposing changes in luminance (i.e., an increase in luminance followed by a decrease, or a decrease followed by an increase) of 20 candelas per square metre (cd.m-2) or more (see notes 1 and 2). This applies only when the screen luminance of the darker image is below 160 cd.m-2. Irrespective of luminance, a transition to or from a saturated red is also potentially harmful. Isolated single, double, or triple flashes are acceptable, but a sequence of flashes is not permitted when both the following occur: i. the combined area of flashes occurring concurrently occupies more than one quarter of the displayed (see note 3) screen area; and ii. there are more than three flashes within any one-second period. For clarification, successive flashes for which the leading edges are separated by 9 frames or more are acceptable, irrespective of their brightness or screen area. Notes: 1. A luminance voltage of 234 mV results in light output of 20.1 cd.m-2. If the brighter image of a flash or pattern is above this level, then it is potentially harmful if the light output between the darker and brighter images differs by 20 cd.m-2 or more. 2. A luminance voltage of 631 mV results in light output of 160 cd.m-2. If the darker image of a flash or pattern is below this level, then it is potentially harmful if the light output between the darker and brighter images differs by 20 cd.m-2 or more. Cheers Si. ======================= Simon Harper University of Manchester (UK) Human Centred Web Lab: http://hcw.cs.manchester.ac.uk My Site: http://hcw.cs.manchester.ac.uk/people/harper/ My Diary (Web): http://hcw.cs.manchester.ac.uk/people/harper/ phpicalendar/week.php My Diary (Subscribe): http://hcw.cs.manchester.ac.uk/diaries/harper/ SimonHarper.ics
Received on Thursday, 14 May 2009 18:35:57 UTC