M Y N D E X
We are currently researching perceptual contrast for assessing legibility and accessibility on graphically rich web pages and computer displays. Below are links to some of the early live experimental pages, evaluating the issue(s) in detail.
WEB APPS & STUDIES
PerceptEx Δγ The Web Perception Experiment
COMING SOON: a public study that you can be involved in! Currently under development, it will evaluate how people perceive content in real world situations. Stay-tuned here as we prepare to launch that project.
CVD Simulator ▴⧫▴ Color Vision Deficiency Simulation
NEW: We developed this new web app to simulate how someone with Color Vision Deficiency** sees the world. We accurately simulate Protanopia, Deuteranopia, and Tritanopia using the Brettel '99 &'97 models. We also present some experimental models, such as Blue Cone Monochromacity. www.myndex.com/CVD/
While the Brettel model is accurate for how certain types of CVD perceive the world, we also created an experimental model of how CVD specifically perceives sRGB monitors. Because tristimulus monitors only display three specific colors in various combinations, most of the colors that you see are metameric and non-spectral. So we also developed this sRGB CVD Simulator to simulate how someone with protanopia, deuteranopia, or tritanopia specifically sees sRGB monitors. www.myndex.com/CVD/sRGBCVD
**Color Vision Deficiency is sometimes referred to as "color blind,"
though that is not accurate except in some very rare cases.
Perceptual Contrast ☼ Live Contrast Experiments 2019
These experiments relate to WCAG open issue number 695 and others on GitHub.#695 some pre-prints also on ResearchGate. For questions contact user Myndex on Github. (aka Color Science Researcher: Andrew Somers).
Below are links to some of the early live experimental pages, evaluating the issue(s) in some detail.
Please be advised: The experiment pages listed below are using fonts sized in REM and are thus NOT responsive. They are intended for desktop/laptop use, or use in our test app. Most require a monitor 1024px to 1200px wide to view.
Most Recent Experiments First
Brief Commentary on Contrast
and the WCAG Accessibility Standards.June 2019:
Interestingly, the W3C/WCAG math is similar to a basic Weber contrast in terms of a perception curve when in a totally DARK environment (such as a bedroom at night). Of course the problems described are present in typical and high ambient lighting.
One of the curiosities with the WCAG math is the addition of a 0.05 "flare" component to both sides of the simple contrast equation:
(L1 + 0.05) / (L2 + 0.05) This appears to do little except distort contrast by marginally pushing ratios slightly toward 1:1 (if you eliminate the L luminance terms, you get 0.05/0.05 = 1:1).
It is not a particularly useful way to boost contrast or limit low contrast. While it does help to slightly enhance contrast in dark color pairs, dark color pairs is where the overall WCAG still suffers most, especially in high ambient lighting conditions. Indeed this math generates some contrast figures that are ultimately illegible in real world conditions. (Paradoxically, the math also rejects some color pairs that are perfectly legible).
One of several alternatives, Hwang-Peli's Modified Weber adds the flare component to only one side, the denominator, as:
(Llight - Ldark) / (Llight + 0.05)
In our experiments in real world conditions (including mobile devices) we've found that an offset of 0.1 is more useful than 0.05 :
(Llight - Ldark) / (Llight + 0.1)
We discuss this modified Weber in this post in the GitHub discussion. This method provides a superior and more robust contrast assessment than the current WCAG methods.
Advances in Perception: Our ongoing research is working with a new set of equations & algorithms that are based on human visual perception. Beyond providing a reliable and robust assessment of contrast for accessibility guidelines for graphically rich web content, we anticipate further development of the concepts will lead to better environmental responsiveness for computer display devices in general.