WebAIM - Web Accessibility In Mind

E-mail List Archives

Re: Color Contrast and Gradients

for

From: Monique Brunel
Date: May 23, 2012 8:45AM

Le 23/05/2012 14:24, Elle a écrit :
> David:
>
> We test highest, midpoint, and lowest points of a gradient to ensure proper
> color contrast. However, we also look for readability on any text over
> background images (something else to consider during this conversation).
>
>
> Cheers,
> Elle

Hi,

Just a feedback on this ...

I am dyslexic and very sensitive to the brightness (I can not easily
read white text on black background), and more, my speed of
accommodation to light variations is very small ... also, whatever the
color of the gradient and color of text, reading is very difficult for
me, sometimes impossible (I have also the same problems on paper, such
as magazines or flyers).

Best regards,
Monique

> On Tue, May 22, 2012 at 11:57 PM, John Foliot< <EMAIL REMOVED> > wrote:
>
>> David Ashleydale wrote:
>>>
>>> Do any of you have any tips on color contrast considerations when a
>>> piece
>>> of text's background color isn't solid, but is a gradient? Off the top
>>> of
>>> my head, I was thinking that I could just measure the contrast at the
>>> highest and lowest points of the letters and ensure that the contrast is
>>> sufficient there. Or perhaps I could just do the midpoint of the text?
>>
>> FWIW, this is how we are dealing with this issue internally.
>>
>> Assume that the gradient goes from lightest at the top to darkest at the
>> bottom. We look to the "middle" range of the color and ensure that the
>> lettering that is on top of that gradient has at least 51% "below" that
>> middle line: in other words more than 50% of the letter is on a background
>> that meets or exceeds the minimum.
>>
>> We rely on a known phenomenon where the human eye fills in "missing data"
>> in
>> the same way that you can figure out what I wrote here: I Lv Nw Yrk
>>
>> It is essentially an optical illusion, although not of the "trick" variety:
>> none-the-less because there is enough letter on the dark-enough contrast,
>> most human eyes will make up the difference and you will discern the
>> letter(s) - and because our eyes also group letters as words, that too will
>> re-enforce the overall cognition of the text on the gradient.
>>
>> FWIW.
>>
>> JF


--
Accessibilité et qualité des sites Web
Monique Brunel - Conférences - Ateliers - Conseil
| http://blog.webatou.info | Tél. +32(0)473 25 81 94
| www.opquast.com | www.openweb.eu.org | www.mozilla-belgium.org |