FW: [WebAIM] How were the WCAG contrast ratios determined

Information in the forward below from WebAIM indicating the plan to do some research on contrast and font sizes, etc. with people that have low vision or color perception disabilities. 

Jonathan

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Jonathan Avila
Chief Accessibility Officer
SSB BART Group 
jon.avila@ssbbartgroup.com

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-----Original Message-----
From: WebAIM-Forum [mailto:webaim-forum-bounces@list.webaim.org] On Behalf Of Jared Smith
Sent: Thursday, February 11, 2016 10:10 PM
To: WebAIM Discussion List
Subject: Re: [WebAIM] How were the WCAG contrast ratios determined

Sean Curtis wrote:
> Does anyone have any historical information about how the ratios for 
> A, AA, and AAA were determined? Were they based on the contrast of 
> screens, or on how light and vision works?

The formulas were derived from the sRGB color space proposal document [1] and IEC/4WD 61966-2-1 (couldn't find a copy of this). These were both authored in 1996.

Think for a moment about the screen you were using in 1996. There's no doubt that modern screens are brighter, have higher contrast, better color resolution, and MUCH higher pixel resolution. All of these things can decrease the impact on readability of lower luminosity contrast as derived from RGB color values.

We regularly conduct an informal poll as part of our trainings by showing various colors on screen and ask participants to guess which pass and fail WCAG. Almost universally folks choose several colors that fail as being the ones that pass.

To help get some measurable data on the actual user impacts (with a focus on users with low vision and color blindness) of color combinations (and font sizes, faces, etc.), WebAIM will be conducting some research on this topic in the near future to see, in part, how well the WCAG contrast formula thresholds relate to actual accessibility on modern devices.

Jared

[1] https://www.w3.org/Graphics/Color/sRGB.html

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Received on Friday, 12 February 2016 14:54:22 UTC