additional agenda item

 

The question about whether we should have an upper limit on our 2.3
guideline regarding seizure disorders.

 

It was pointed out that current guidelines run 2 or 3 to 50 or 60 hz.    But
2.3 has no upper bound even though seizure disorder sensitivity drops off at
50 to 60 hz and above.   

 

However since we are talking about web content.   It will be a fast machine
that can render content at 100 frames per second to create a 50 hz flash
rate.

 

But I would like to check the thinking on this at the meeting just to be
sure. 

 

Should we add an upper "permissive " threshold? 

 

 

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 

 

-----Original Message-----

From: Andi Snow-Weaver [mailto:andisnow@us.ibm.com] 

Sent: Wednesday, April 12, 2006 4:29 PM

To: gv@trace.wisc.edu

Subject: Flashing content - WCAG 2.0 and 508

 

 

Hi Gregg,

 

In IBM, we are working on incorporating the WCAG 2.0 requirements into our
current checklist. Ultimately, we will have one checklist in IBM that our
developers can follow that will ensure conformance with both 508 and WCAG
2.0. Our challenge, though, is to ensure that we do it in such a way that we
can still extract out conformance with either 508 or WCAG. For the most part
this seems doable (although not simple :-) ).

 

There don't appear to be any cases where meeting a 508 requirement might
cause you to fail WCAG 2.0 or vice versa except one - flashing content (WCAG
2.0 checkpoint 2.3.1 and 508 1194.22 j).

 

508 says you can't have any flickering at all that is greater than 2 Hz and
less than 55 Hz. WCAG 2.0 is less restrictive than 508 in that it doesn't
prohibit all flickering - only the flickering of a certain size and between
certain color differences. But WCAG 2.0 doesn't put an upper bound on the
flickering as 508 does (55 Hz). So, for the most part, if you meet 508, I
think you would also meet WCAG 2.0 unless you were flickering at 55 Hz or
more. In this case, you would meet 508 but might not meet WCAG 2.0.

 

I think the only way for flickering content to meet both WCAG 2.0 and 508 is
as follows:

- flickering conten at at 2 Hz or below conforms to both WCAG 2.0 and 508

- there can be no flickering content at more than 2 Hz and less than 55 Hz

- if there is flickering content at more than 55 Hz, it must not violate
either the general or red flash thresholds

 

Do you agree?

 

In the spirit of harmonization, is there any chance we could put the 55 Hz
upper bound in 2.3.1 so that if you meet 508 in this area, you would also
meet WCAG 2.0? When the Access Board refreshes 508, we have a chance to get
them to adopt WCAG 2.0. If they do that, then we could do an errata on WCAG
2.0 to remove the upper bound on 2.3.1.

 

Andi

andisnow@us.ibm.com

IBM Accessibility Center

(512) 838-9903, http://www.ibm.com/able

Internal Tie Line 678-9903, http://w3.austin.ibm.com/~snsinfo

 

 


Gregg

------------------------

Gregg C Vanderheiden Ph.D. 
Professor - Depts of Ind. Engr. & BioMed Engr.
Director - Trace R & D Center 
University of Wisconsin-Madison 
< <http://trace.wisc.edu/> http://trace.wisc.edu/> FAX 608/262-8848  
For a list of our list discussions http://trace.wisc.edu/lists/

The Player for my DSS sound file is at http://tinyurl.com/dho6b 

 <http://trace.wisc.edu:8080/mailman/listinfo/>