• Easy Intro to APCA? This is the simple, plain-language introduction to APCA that you've been looking for. This is an ideal place to start and is an easier version of WhyAPCA.

• linktr.ee/Myndex In an effort to pare down the mountain of material, this linktree is composed of the essential links, with the most basic at the top.

• Basic Tool & Quickstart Docs The basic APCA demonstration tool with live font examples and general design guidance for designers and developers.
• APCA Readability Criterion In depth guidelines for accomodating user needs regarding visual content, includes testing methods, conformance models, best practices, and more. Public Working Draft.

Why did APCA become popular? Because it follows actual science, including the science of readability with visual impairments. APCA promotes actual accessibility. Yet there have been unfounded rumors that it has not been peer reviewed or tested, when there is a growing corpus of third party reviews, including journal published, as can be seen at APCA Reviewed.

• Why APCA? This brief introduction into APCA describes how it solves the problems of WCAG_2 contrast. See Easy Intro to APCA? for the plain language version.
• APCA in a Nutshell Basic overview for using APCA, including simple use-case based conformance levels. This is a bare bones version, for the deeper dive see APCA Readability Criterion
• APCA FAQ APCA Frequenty Asked Questions (in development)
• Easy Intro to APCA? This is the simple plain-language introduction to APCA that you've been looking for. This is a simpler version of WhyAPCA above.

• APCA W3 Functions/API Using the API of the APCA W3 package.
• Links To Tools & Apps Some of the tools,apps, and design systems that have adopted APCA.
• Main Readme Doc (HTML version) Includes the math and walkthroughs, and additional resources.
• Documentation Index An index of APCA related documentation relating to code libraries.
• The Main List This page, i.e. you are HERE.

• APCA Forum Discussion, questions, and community contributions.
• Tangled Web The Myndex Research tech blog.
• Social
  • Myndex on Twitter
  • Myndex on Mastodon
  • Andrew on LinkedIn
  • Inclusive Reading Technologies on Twitter
  • Inclusive Reading Technologies on Mastodon

Maths! Theory! Vision Science! Photons on Parade!

• The Realities And Myths Of Contrast And Color A plain language, in-depth primer to vision, color, and contrast for design, with an emphasis on typography and readability needs. Published in Smashing Magazine.
• The base APCA-W3 formula in LaTeX math for your viewing and calculating pleasure.
• Regarding Exponents Some notes and explaination regarding the powercurve exponents.
• Standard Observer Model Draft standardized environment.

• Repo List List of APCA and related respositories.
• Important Change Notices Current constants refer to 0.0.98G-4g
• List Your Tool Here! Have you created a tool using APCA or BridgePCA? Let us know!
  • Third Party Tools Letting us know gets your tool onto the official third party tool listing.
• APCA™ Integration Compliance Discusses levels of implementation.
• How to Contribute Contributions welcome — in particular we need to redesign the apcacontrast.com tool for responsiveness, set up rollup for builds, and a few other things. Help wanted!

• APCA Documentation Repository The docs repo and forum for APCA and SACAM
• APCA W3 Repository The W3 version code repo for web content
• Max Contrast A very simple, APCA compatible text color flipper. Flips from black to white text at middle contrast.
• Inclusive Reading Technologies The repo for IRT and the APCA Readability Criterion.
• Bridge PCA Repository Bridge PCA - the WCAG 2 compatible version
• DeltaPhiStar Repository A simplified general purpose contrast algorithm using L*
• Color Parsley Repository Fast and easy color string parsing — a NodeJS dependency for many of the SAPC libraries.
• SeeStars Repository A microlibrary for calculating L*
• APCA Technical Clarifications Corrections to a third-party analysis
• FancyFontFlipping Repository At what point should text flip from black to white? This repo houses experiments and discussion of "font flipping". See also Max Contrast, above.
• Tiny Trim A CSS sheet of terse utility classes for rapid layout adjustments during development.

• APCA Use Cases, Conformance, Research, and Glossary Discussion of use cases for text and non-text elements, and references to the relevant research. Conformance considerations and rational basis for guidelines.
• Inline text links theory and practice Draft guidance regarding link identification.
• WCAG 2 vs APCA Comparisons Direct head to head comparisons.
• Discuss Maximum Contrast Here
• HDR Displays, Dark Mode Color Palettes, and APCA
• Glossary: Terminology Emerging From APCA Research
• Contrast Arising from Text Spatial Frequency

The problems of 4.5:1 as a target for a guideline is that it not only impact those with impairments, but impacts standard vision as well. WCAG 2 contrast SCs affect 100% of sighted users. The inherent problems with the WCAG 2 contrast math have been known for some time and widely critisized. Including studies by others showing that color insensitive types are not well served.

The WCAG 2 contrast specs often cause enough problems for designers that it is ignored and today, some 86% of websites are failing WCAG_2 contrast per an automated survey—though some of these failures are not due to poor actual accessibility, but due to the perceptual inaccuracies of WCAG_2 contrast.

The unfortunate end result is a grave distrust of the WCAG 2.x accessibility guidelines overall, despite the many other important aspects of those guidelines.

• APCA Demonstrator The APCA contrast technology demonstrator—it's not as slick as a production tool, but presents the essential functions for design guidance.
• Bridge-PCA Calculator Bridge-PCA or BPCA is a drop-in replacement for WCAG_2 contrast that is backwards compatible with the existing guideline, but is using APCA technology for improved readability.
• Color Vision Deficiency Simulator This simulator demonstrates the way someone with a Color Vision Deficiency (incorrectly labeled "color blind") sees colors. This simulator uses the clinically accurate Brettel/Viénot model of CVD simulation for the primary (deuteranopia, protanopia, tritanopia) and there is an experimental blue cone monochromacy sim, based on the Brettel/Viénot concepts.

• The Realities And Myths Of Contrast And Color This popular article is an in-depth primer to vision, color, and contrast for design, written in the most plain language way possible. Features an emphasis on typography and readability needs. Published by Smashing Magazine.

• Better reading on the web Published by UX Collective (uxdesign.cc). This article discusses and demonstrates the problems with automated testing and WCAG 2 contrast math, methods, and guidelines.

• Published at Tangled Web (TangledWeb.xyz):

  • Small Text is Medium's Large Fail The Medium platform has a lot of good features going for it, yet it literally ignores visual accessibility. For a platform that is entirely based around readable content, one would think that it'd be close to State of the Art, instead of the State of Unreadable.
  • Hats off to ALL CAPS Myth-busting the misunderstandings regarding accessibility: are dyslexia fonts useful and the shift in using ALL UPPERCASE LETTERS for various text elements.
  • Getting the Wrong, Right? What does it mean to get something right, if the underlying foundation of that thing is ultimately wrong?
  • Busy Background Breaks Bulletin Examples of how to destroy readability by choosing the wrong image as a background. And also, how to fix it.
  • Please Stop Using Grey Text Debunking one of the worst myths regarding design contrast. This article went viral in early 2022.
  • What's Red & Black & Also Not Read? Do the WCAG 2 Contrast Guidelines help users with color vision issues? While this is a widely held belief, the truth may surprise you.
  • A Contrast of Errors A look into the history of the WCAG 2 contrast guidelines and some of the problems created by them, and a discussion of the proposed replacement, the APCA (Accessible Perceptual Contrast Algorithm).

• Contrasting Theories Article at Tangled Web
• A Contast of Contrasts Article at Tangled Web
• Luminance is King LinkedIn post on the importance of luminance for reading.
• Human Contrast Sensitivity Curve LinkedIn post on the nature of human contrast sensitivity.
• Legally Readable LinkedIn post on the value of actual accessibility vs arbitrary law.

Mini articles on technical topics, with examples

• brintness is an integer brightness/lightness/darkness calculation. This is part of an experiment in estimating a perceived brightness while remaining in integer math and using bitshifts to maximize performance.

• Kelly's 22 Colors of Some Contrast (revised) An object of Kelly's 22 colors, as for "maximum contrast", I do not endorse that claim.

• Phi Alternate Expression a formula for phi, reduced to a positive exponent, multiplication, and addition...

• What's Up With Markdown GitHub Flavored Markdown Cheat Sheet.

• Three Part Series on WCAG 2 contrast problems with comparisons to perceptually uniform models.

  • Part I: Orange You Wondering About Contrast? Answering some contrast questions, and demonstrating a real solution to the infamous orange conundrum.
  • Part II: The Lighter Side of Dark Backgrounds An article comparing some parts of APCA with the old WCAG 2 contrast methods, demonstrating how WCAG_2 contrast does not help color vision types.
  • Part III: WCAG 2 vs APCA Contrast Shootout Answering some recent questions regarding APCA, with comparisons and examples of the old (WCAG 2 1.4.3) and the future WCAG 3 / APCA.

• COLORSPACES-The Primal Frontier A brief Look at the math that helps model how we see.

• How Many Colors in a Bushel? Just "how many" colors are there? Is that even an answerable question?

• Part I: For The Luv of Color An article comparing CIE Lab and Luv colorspaces.

• Part II: Will Work for Color A follow-up article on working spaces and related considerations, including how ICC profiles may not be a great choice for web due to their inefficiency. Introduces the concept of "Web Working Spacelets".

• colorPalette.js aka Kelly's 22 colors.

• A Listing of Significant (Legacy) Threads
  • These were some of the larger, in-depth issue threads & posts created on GitHub including the influential thread #695. These posts contain useful information and research. Some of the information here may be superseded as some of these threads date back to the beginnings of the contrast research project.

Most of the important posts are being collated into the Illuminated Repo.

For responses to common technical misconceptions about APCA, please see the APCA Technical Clarifications repository.

• Funny you mention Kodak and Xerox In this response to James Biber's "Theranos, Polaroid and the legacy of dropouts", I touch on the law of unintended consequences as has repeatedly manifested in the development of modern technology.
• Modern Password Theory in a Nutshell A realistic discussion on password security, with a practical approach to reducing crackability.
• Improving SEO with Redirects Your server's case sensitivity and URL redirect strategies can affect your search ranking!

• What's Up With Markdown GitHub flavored Markdown cheat sheet.
• Phi Alternate Expression An alternate expression of the formula for Phi.

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