User Needs - contrast sensitivity

All,
I have been doing a good bit of research related to the contrast
discussions on Issues 9 & 10 (graphics contrast and UI controls contrast).
I updated the research page with what I found.

In our user needs document the section on 2.4.3 Contrast Sensitivity needs
a few additions. other sections of the document discuss which eye
conditions have a particular impairment (acuity, glare, color, field, etc)
and the functional problems caused by the impairment. 2.4.3 lacks this
information. Updating 2.4.3 and the benefits section of Issue 9 & 10 should
address the concerns raised in the comments on these items.

current 2.4.3:

Contrast sensitivity is the ability to detect differences in brightness,
for example, to discern text from its background. A common accessibility
barrier for people with low contrast sensitivity is gray text on a light
background.

Contrast is based on brightness. Colors that look very different (for
example, red, blue, green) can have similar brightness, and not provide
sufficient contrast. Tools
<https://www.w3.org/TR/UNDERSTANDING-WCAG20/visual-audio-contrast7.html#visual-audio-contrast7-resources-head>
are
available to determine the contrast ratio between colors.
new:

Contrast sensitivity is the ability to detect differences in brightness,
for example, to discern text from its background. A common accessibility
barrier for people with low contrast sensitivity is gray text on a light
background. *Contrast sensitivity decreases with age and is concomitant
with many other vision diseases and conditions. Contrast levels should be
the same for text, graphics, and controls.*

Contrast is based on brightness. Colors that look very different (for
example, red, blue, green) can have similar brightness, and not provide
sufficient contrast. Tools
<https://www.w3.org/TR/UNDERSTANDING-WCAG20/visual-audio-contrast7.html#visual-audio-contrast7-resources-head>
are
available to determine the contrast ratio between colors.

​Current Benefit section for Issues 9 & 10: ​

People with low vision often have difficulty perceiving graphics that have
insufficient contrast. This can be exacerbated if the person has a color
vision deficiency that lowers the contrast even further. Providing a relative
luminance
<http://www.w3.org/TR/2008/REC-WCAG20-20081211/#relativeluminancedef>
(lightness) difference of 4.5:1 or greater can make these items more
distinguishable when the person does not see a full range of colors and
does not use assistive technology.

When non-text content is larger, a color contrast of 3:1 or greater can be
sufficient for perception by people with moderately low vision.

*In short, contrast levels should be the same for text, graphics, and
controls.*

-- 
Jim Allan, Accessibility Coordinator
Texas School for the Blind and Visually Impaired
1100 W. 45th St., Austin, Texas 78756
voice 512.206.9315 <(512)%20206-9315>    fax: 512.206.9264
<(512)%20206-9264>  http://www.tsbvi.edu/
"We shape our tools and thereafter our tools shape us." McLuhan, 1964