2.3 Suggested edits for guidelines 2.3 on Seizure disorders

Here are some suggested edits for the WCAG Photosensitive Epilepsy guideline
Definition.  

They are to clarify some ambiguous parts but do not change the guidelines.


Gregg

 -- ------------------------------ 
Gregg C Vanderheiden Ph.D. 
Professor - Ind. Engr. & BioMed Engr.
Director - Trace R & D Center 
University of Wisconsin-Madison 
The Player for my DSS sound file is at http://tinyurl.com/dho6b 


Note:  All modified content segments are enclosed in double braces {{}}




definition for "general flash threshold"


[old definition...]

general flash threshold 
A sequence of flashes or rapidly changing image sequences where both the
following occur:

1.  the combined area of flashes occurring concurrently (but not necessarily
contiguously) occupies more than one quarter of any {{335 x 268}} pixel
rectangle anywhere on the displayed screen area when the content is viewed
at 1024 by 768 pixels and

2.  there are more than three flashes within any one-second period.

Note: For the general flash threshold, a flash is defined as a pair of
opposing changes in brightness of 10% or more of full scale white
brightness, where brightness is calculated as {{.2126*R + .7152*G + .0722B
using linearized R, G, and B values. Linearized-X = (X/FS)^2.2 where FS is
full scale (usually 255 today)}}. An "opposing change" is an increase
followed by a decrease, or a decrease followed by an increase.

[end of old definition]


[new definition...]

general flash threshold 
sequence of flashes or rapidly changing image sequences where both the
following occur:

1.  the combined area of flashes occurring concurrently (but not necessarily
contiguously) occupies more than one quarter of any {{341 x 256}} pixel
rectangle anywhere on the displayed screen area when the content is viewed
at 1024 by 768 pixels and

2.  there are more than three flashes within any one-second period.

Note: For the general flash threshold, a flash is defined as a pair of
opposing changes in brightness of 10% or more of full scale white
brightness, where brightness is calculated as {{0.2126 * ((R / FS) ^ 2.2) +
0.7152 * ((G / FS) ^ 2.2) + 0.0722 * ((B / FS) ^ 2.2). R, G, and B are the
red, green, and blue RGB values of the color; FS is the maximum possible
full scale RGB value for R, G, and B (255 for eight bit color channels); and
the "^" character is the exponentiation operator}}. An "opposing change" is
an increase followed by a decrease, or a decrease followed by an increase.

[end of new definition]


############################################################
definition for "red flash threshold"
also present in body of "How to Meet Success Criterion 2.3.2{{1}}"


[old definition...]

red flash threshold 
A transition to or from a saturated red where both of the following occur:

1.  the combined area of flashes occurring concurrently occupies more than
one quarter of any {{335 x 268}} pixel rectangle anywhere on the displayed
screen area when the content is viewed at 1024 by 768 pixels and

2.  there are more than three flashes within any one-second period.

[end of old definition]


[new definition...]

red flash threshold 
A transition to or from a saturated red where both of the following occur:

1.  the combined area of flashes occurring concurrently occupies more than
one quarter of {{341 x 256}} pixel rectangle anywhere on the displayed
screen area when the content is viewed at 1024 by 768 pixels and

2.  there are more than three flashes within any one-second period.

[end of new definition]

Received on Wednesday, 22 February 2006 07:43:54 UTC