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Re: Color Contrast Question

for

From: Jonathan Whiting
Date: Sep 20, 2017 11:25AM

On Sep 20, 2017 10:43 AM, "Jared Smith" < <EMAIL REMOVED> > wrote:

> The WCAG formula generates the contrast ratios, but these don't align to a
> percent or "times darker" value. The minimum is 1:1 and the maximum is
> 21:1. Your logic would suggest that 1:1 (white on white) means white is one
> times darker than white, and black on white means black is 21 times darker
> than white. That doesn't work. Your phrasing also wouldn't consider light
> text on a black background. And the ratios are not linear - 4:1 is not
> twice as much contrast as 2:1, for example.
>
> In reality the formula doesn't consider many aspects of true contrast and
> perception. WebAIM and others are trying to influence a reconsideration of
> this formula and perhaps the WCAG pass/fail thresholds to better align them
> with human perception. With that said, the WCAG ratios do give a relatively
> accurate measure of *luminance* contrast - and that's pretty important. If
> your colors fall well below the WCAG thresholds, they'll be difficult for
> most anyone to read.
>
> Jared Smith
>
>
>
>
>
> On Wed, Sep 20, 2017 at 8:44 AM, JP Jamous < <EMAIL REMOVED> > wrote:
>
> > Folks,
> >
> >
> >
> > I want to be able to breakdown 4.5:1 and 3:1 into a simple way. Is it
> > correct to state the following?
> >
> >
> >
> > 4.5:1 means that the foreground color should be 4 and a half times darker
> > or
> > lighter than the background color to be seen properly by people with low
> > vision individuals.
> >
> > 3:1 means that the foreground color should be 3 times darker or lighter
> > than
> > the background color to be seen properly by people with low vision
> > individuals.
> >
> > If I am wrong can you correct me please?
> >
> >
> >
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