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<h1 id="title" class="title headerPlus">APCA Readability Criterion</h1>
<p id="irt-state"><a href="https://www.readtech.org/ARC/">ARC Public Beta Draft</a> <time class="dt-published" datetime="2023-03-12">12 March 2023</time></p>
<div class="upR"><p class="info" style="">Content in this resource is still under active development and should be considered beta. It may change, move, antecede, or be deleted with or without notice.</p><img style="" src="./img/safetyManSMALL.png" height="150"></div>
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<p><button id="quickstart" onclick="window.location.href='./tests/visual-readability-contrast/'" ><div>JUMP TO</div>VISUAL CONTRAST QUICK START</button></p>
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<section id="abstract" class="introductory">
<h2 class="headerPlus">EXECUTIVE SUMMARY</h2>
<img src="./img/IRT/IRTtextPaths_v03.svg" alt="IRT logo" style="position: relative; margin: 1em 1.5em; top:0px; float: right; width: 40%;">
<p>The APCA™ Readabiliy Criterion (ARC™) provides a range of evidence-based recommendations for making visual content on self-illuminated displays more accessible to all users, especially users with visual impairments. These guidelines are developed with a thorough understanding and reference to modern peer-reviewed research and scientific consensus in the areas of visual perception and visual reading.</p>
<p>Following these guidelines will address many of the needs of users with low vision, color vision deficiency, and other visual impairments; certain cognitive and learning disabilities; and combinations of these. These guidelines address visual accessibility of applications and content on desktops, laptops, tablets, mobile devices, kiosks, point of sale, and embedded systems.</p>
<p>This specification is expected to be updated regularly to keep pace with changing technology by updating and adding design guides, test-methods, objectives, and guidelines to address new needs as technologies evolve. Several levels of conformance are available to address the diverse nature of digital content, and the specific goals of entities that wish to make formal claims of <a href="#dfn-conformance" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-conformance-1"> conformance</a> to these guidelines.</p>
<section id="background" class="introductory"><h2 class="headerPlus3">History and Purpose</h2>
<p>APCA Readability Criterion (ARC) began as a project to correct well known problems with <abbr title="Web Content Accessibility Guidelines 2">"WCAG 2.x</abbr> contrast specifications, and subsequently evolving into draft guidance for the future <abbr title="World Wide Web Consortium (W3C) Accessibility Guidelines 3">WCAG 3</abbr>. APCA and ARC are intended to integrate with these and other relevant standards. To that end, ARC is designed to follow the general form of WCAG 3 as it develops. This also means ARC includes additional tests and different scoring mechanisms than used previously. As a result, ARC is not backwards compatible with WCAG 2.x.
<p>ARC is an alternative, independent set of guidelines as embodied herein. The expected release date of WCAG 3 is several years in the future, but there is a pressing need today for a perceptually uniform contrast measure. The design community requires a useful contrast guideline capable of calculating for modern design needs, such as dark mode. These APCA Readability Criterion are presented here to bridge this gap, with the aim of improving <em>actual</em> accessibility.</p>
</section>
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<nav id="toc"><h2 class="introductory headerPlus1" id="table-of-contents">Table of Contents</h2>
<p><button id="status-filter-toc" data-status-filter="research,placeholder,deprecated" style="/* padding: 0.5em 1em; font-size: 1.3em; font-weight:700; background: #FF6; border-radius: 0.75em */">Show Hidden</button></p>
<ol class="toc"><li class="tocline"><a class="tocxref abstract" href="#abstract"> Executive Summary</a>
<ol class="toc"><li class="tocline"><a class="tocxref abstract" href="#background">History and Purpose</a></li>
<li class="tocline"><a class="tocxref abstract" href="#sotd">Status of This Document</a></li>
</ol></li>
<li class="tocline"><a class="tocxref" href="#introduction"><bdi class="secno">1. </bdi>Introduction</a>
<ol class="toc">
<li class="tocline"><a class="tocxref" href="#about-apca-readability-criterion"><bdi class="secno">1.1 </bdi>About APCA & ARC</a></li>
<li class="tocline"><a class="tocxref" href="#section-status-levels"><bdi class="secno">1.2 </bdi>Section Status</a></li>
<li class="tocline"><a class="tocxref" href="#goals-and-requirements"><bdi class="secno">1.3 </bdi>Objectives</a></li>
</ol></li>
<li class="tocline"><a class="tocxref" href="#normative-requirements"><bdi class="secno">2. </bdi>Normative</a></li>
<li class="tocline"><a class="tocxref" href="#criterion"><bdi class="secno">3. </bdi>Summary<div>Visual Presentation</div> </a>
<ol class="toc">
<li class="tocline"><a class="tocxref" href="#visual-contrast-map"><bdi class="secno">3.1 </bdi>Visual Contrast<div>Guidelines Map</div></a></li>
</ol></li></li>
<li class="tocline"><a class="tocxref" href="#visual-contrast-text"><bdi class="secno">4. </bdi>Visual Contrast<div>Text & Fonts </div></a>
<ol class="toc">
<li class="tocline"><a class="tocxref" href="#objective-lightness"><bdi class="secno">4.1 </bdi>Objective: <div>Text Lightness Contrast</div></a></li>
</ol></li>
<li class="tocline"><a class="tocxref" href="#nontext-contrast"><bdi class="secno">5. </bdi>Visual Contrast<div>Non-Text & DataViz</div></a></li>
<li class="tocline"><a class="tocxref" href="#user-integration"><bdi class="secno">6. </bdi>User Integration<div>Visual UX</div></a></li>
<li class="tocline"><a class="tocxref" href="#conformance"><bdi class="secno">7. </bdi>Conformance</a>
<ol class="toc">
<li class="tocline"><a class="tocxref" href="#conformance-levels"><bdi class="secno">7.1 </bdi>Conform Levels</a>
<ol class="toc">
<li class="tocline"><a class="tocxref" href="#bronze"><bdi class="secno">7.1.1 </bdi>Bronze</a></li>
<li class="tocline"><a class="tocxref" href="#silver"><bdi class="secno">7.1.2 </bdi>Silver</a></li>
<li class="tocline"><a class="tocxref" href="#gold"><bdi class="secno">7.1.3 </bdi>Gold</a></li>
</ol></li>
<li class="tocline"><a class="tocxref" href="#use-cases-levels"><bdi class="secno">7.2 </bdi>Use Cases & Levels</a>
<ol class="toc">
<li class="tocline"><a class="tocxref" href="#text-use-cases"><bdi class="secno">7.2.1 </bdi>Text Use Cases</a></li>
<li class="tocline"><a class="tocxref" href="#non-text-use-cases"><bdi class="secno">7.2.2 </bdi>Non-Text Use Cases</a></li>
<li class="tocline"><a class="tocxref" href="#mode-use-cases"><bdi class="secno">7.2.3 </bdi>Mode Use Cases</a></li>
</ol></li>
<li class="tocline"><a class="tocxref" href="#defining-conformance-scope"><bdi class="secno">7.3 </bdi>Conformance Scope</a>
<ol class="toc">
<li class="tocline"><a class="tocxref" href="#top-down-scope"><bdi class="secno">7.3.1 </bdi>Top Down Scope</a></li>
<li class="tocline"><a class="tocxref" href="#bottom-up-scope"><bdi class="secno">7.3.2 </bdi>Bottom Up Scope</a></li>
<li class="tocline"><a class="tocxref" href="#middle-out-scope"><bdi class="secno">7.3.3 </bdi>Middle Out Scope</a></li>
</ol></li>
<li class="tocline"><a class="tocxref" href="#conformance-requirements"><bdi class="secno">7.4 </bdi>Requirements</a></li>
<li class="tocline"><a class="tocxref" href="#conformance-certification"><bdi class="secno">7.5 </bdi>Certification</a></li>
</ol>
</li>
<li class="tocline"><a class="tocxref" href="#glossary"><bdi class="secno">8. </bdi>Glossary</a>
<ol class="toc">
<li class="tocline"><a class="tocxref" href="#glossary-apca-vision"><bdi class="secno">8.1 </bdi>APCA & Vision Terminology</a></li>
<li class="tocline"><a class="tocxref" href="#glossary-specs"><bdi class="secno">8.2 </bdi>Specification Terms</a></li>
</ol> </li>
<li class="tocline"><a class="tocxref" href="#references"><bdi class="secno">9. </bdi>References</a>
<ol class="toc">
<li class="tocline"><a class="tocxref" href="#normative-references"><bdi class="secno">9.1 </bdi> Normative</a></li>
<li class="tocline"><a class="tocxref" href="#supporting-references"><bdi class="secno">9.2 </bdi> Supporting</a></li>
<li class="tocline"><a class="tocxref" href="#informative-references"><bdi class="secno">9.3 </bdi> Informative</a></li>
<li class="tocline"><a class="tocxref" href="#perspective-references"><bdi class="secno">9.4 </bdi> Perspective</a></li>
</ol>
</li>
<li class="tocline"><a class="tocxref" href="#guidelines-development-methodology"><bdi class="secno">A. </bdi>Guidelines <div>Development</div></a>
<ol class="toc">
<li class="tocline"><a class="tocxref" href="#guidelines-research"><bdi class="secno">A.1 </bdi>Methodology</a></li>
</ol>
</li>
<li class="tocline"><a class="tocxref" href="#differences-from-wcag-2-x"><bdi class="secno">B. </bdi>Differences from WCAG 2.x</a>
<ol class="toc">
<li class="tocline"><a class="tocxref" href="#objectives"><bdi class="secno">B.1 </bdi>Objective Model</a></li>
</ol>
</li>
<li class="tocline"><a class="tocxref" href="#change-log"><bdi class="secno">C. </bdi>Change log</a>
<ol class="toc">
<li class="tocline"><a class="tocxref" href="#change-lego"><bdi class="secno">C.1 </bdi>Change lego</a></li>
</ol>
</li>
<li class="tocline"><a class="tocxref" href="#acknowledgements"><bdi class="secno">D. </bdi>Acknowledgements</a>
<ol class="toc">
<li class="tocline"><a class="tocxref" href="#special-thanks"><bdi class="secno">D.1 </bdi> Special thanks </a></li>
</ol>
</li>
</ol>
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<section id="sotd" class="introductory"><h2 class="headerPlus3">Status of This Document</h2>
<p>This is a draft document and may be updated, replaced, or superseded by other documents at any time. This document should only be referred to as a work in progress.
</p>
<p>To comment, <a href="https://github.com/Myndex/SAPC-APCA/discussions/new/choose"> start a discussion in the SAPC-APCA GitHub repository</a>.
It is free to create a GitHub account to start discussions and file issues.</p>
<p>Publication as an Editor's Draft does not imply endorsement by <abbr title="Inclusive Reading Technologies">IRT</abbr>.</p>
</section>
<details>
<summary>More details about this document</summary>
<dl>
<dt>Current unpublished draft version:</dt>
<dd>
<a class="u-url" href="https://A11yReadTech.github.io/ARC/">A11yReadTech.github.io/ARC/</a>
</dd>
<dt>Latest published working draft:</dt>
<dd>
<a href="https://www.readtech.org/ARC/">www.readtech.org/ARC/</a>
</dd>
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<dt>Editor:</dt><dd class="editor p-author h-card vcard">
<a class="ed_mailto u-email email p-name" href="mailto:perceptex@myndex.com">Andrew Somers</a> (<span class="p-org org h-org">IRT</span>)
</dd>
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<dt>Project Manager:</dt>
<dd class="editor p-author h-card vcard">
<a class="ed_mailto u-email email p-name" href="mailto:info@readtech.org">Mike Anderson</a> (<span class="p-org org h-org">IRT</span>)
</dd>
<dt>ARC (Readability Guidelines) Feedback:</dt>
<dd>
<a href="https://github.com/A11yReadTech/ARC/">GitHub A11yReadTech/ARC</a>
(<a href="https://github.com/A11yReadTech/ARC/discussions/">ARC open discussions</a>,
<a href="https://github.com/A11yReadTech/ARC/issues/">ARC beta issues</a>)
</dd>
<dt>APCA Algorithm Feedback:</dt>
<dd>
<a href="https://github.com/Myndex/SAPC-APCA/">GitHub Myndex/SAPC-APCA</a>
(<a href="https://github.com/Myndex/SAPC-APCA/discussions/">APCA open discussions</a>,
<a href="https://github.com/Myndex/SAPC-APCA/issues/">APCA beta issues</a>)
</dd>
</dl>
</details>
<p class="copyright">
<a href="/LGL/?tn=copyright">Copyright</a> © 2021-2023 by <a href="https://www.readtech.org/"><abbr title="Inclusive Reading Technologies">IRT</abbr></a><sup>™</sup>. All Rights Reserved.<br>
<a href="/LGL/">Legal:</a> <a href="/LGL/?tn=disclaimers">Liability</a>, <a href="/LGL/?tn=trademarks">Trademarks</a>, <a href="/LGL/?tn=patents">Patents</a>, <a href="/LGL/?tn=license">License & Use</a>
</p>
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<section class="informative" id="introduction">
<div class="addition statusStatic floatAddition review"><a href="#section-status-levels" class="status-link"><strong>Review</strong></a></div>
<div class="header-wrapper "><h2 id="x1-introduction" class="headerPlus"><bdi class="secno">1. </bdi>INTRODUCTION</h2><a class="self-link" href="#introduction" aria-label="Permalink for Section 1."></a></div>
<p class="informative-statement"><em>This section is advisory only, meaning it is <a href="#dfn-informative" class="internalDFN" data-link-type="dfn">informative</a> and non-normative.</em></p>
<div class="note" id="issue-container-generatedID"><div role="heading" class="ednote-title marker" id="h-ednote" aria-level="3"><span class="noteHeading">Development Note</span><a class="self-link" aria-label="§" href="#issue-container-generatedID"></a></div><div class="">
<p>The current proposal for APCA and ARC is made up of several divisions, including:</p>
<ul><li>APCA Based Tools • provide perceptually uniform, objective assessment of contrast</li>
<li>How-tos • Tutorial guides for planning and implementing design strategies</li>
<li>Objectives • Target accommodation goals, serving user needs</li>
<li>Tests • Specific test methods, techniques, and defined criterion for measuring and conforming to guidance</li>
</ul>
</div>
</div>
<details class="summary">
<summary>Plain language summary of <q>Introduction</q></summary>
<p>The APCA Readability Criterion (ARC) is a newer standard based on the Accessible Perceptual Contrast Algorithm, which provides significant improvements over the older Web Content Accessibility Guidelines (WCAG) 2.2. ARC is intended to eventually integrate into other standards such as ISO and WCAG 3.</p>
<p>What’s new in APCA/ARC?</p>
<ul>
<li>APCA/ARC includes math that provides results in accordance with human vision, and better accommodates visual impairments.</li>
<li>It includes mobile and desktop applications, along with web content.</li>
<li>It has new guidelines and new tests that improve readability but also improve design flexibility.</li>
<li>It has new scoring with use cases to define critical content vs unimportant content.</li>
</ul>
</details>
<section id="about-apca-readability-criterion"><div class="header-wrapper marker"><h3 id="x1-1-about-apca-readability-criterion" class="headerPlus3 "><bdi class="secno">1.1 </bdi>About APCA Readability Criterion </h3><a class="self-link" href="#about-apca-readability-criterion" aria-label="Permalink for Section 1.1"></a></div>
<p>The APCA Readability Criterion (ARC) is a modern set of design guidelines or visual content utilizing the Accessible Perceptual Contrast Algorithm (APCA), which is tuned for perceptual uniformity of text and non-text elements, as displayed on a self-illuminated monitor or device.</p>
<p>APCA&ARC provide significant improvements over older methods and guidelines such as the Web Content Accessibility Guidelines (WCAG) 2.x. and other similar standards. The improvements include more robust readability in a wider variety of environments, and on a wider variety of displays and devices. Also, while other methods fail to calculate for dark mode correctly, APCA is well-able to calculate reasonable values here.</p>
<p>These improvements are achieved by referencing and implementing the very latest peer-reviewed vision science, as well as integrating with modern, scientific-consensus readability research. Please see the bibliography for references.</p>
<p>ARC is intended to eventually integrate into other standards such as ISO and the future WCAG 3. As such, you may notice that some aspects of the documents here are presented similarly to those in the emerging WCAG 3. This should come as no surprise, as the authors of ARC are also actively working as part of the task force&subgroups developing WCAG 3. However we want to stress that the ARC are a separate, independent set of guidelines, and are not presently an official recommendation, and should be referenced only as a work in progress.</p>
</section>
<section id="section-status-levels"><div class="header-wrapper"><h3 id="x1-2-section-status-levels" class="headerPlus3 marker"><bdi class="secno">1.2 </bdi>Section status levels</h3><a class="self-link" href="#section-status-levels" aria-label="Permalink for Section 1.2"></a></div>
<p>Sections of this document are assigned a status, <em>approximately</em> following the present, draft patterns of WCAG 3. This status is used to indicate what stage of development the section is at present.</p>
<ul id="status-levels" class="nobull">
<li><strong id="status-deprecated">Deprecated</strong> : Obsolete and no longer supported ••• <em>hidden</em>.</li>
<li><strong id="status-placeholder">Placeholder</strong> : Future content will be here ••• <em>hidden</em>.</li>
<li><strong id="status-research">Research</strong> : Early due-diligence & research phase <em></em>.</li>
<li><strong id="status-development">Development</strong> : An active developing draft, subject to revision.</li>
<li><strong id="status-review">Review</strong> : Public beta ready for broad public review.</li>
<li><strong id="status-mature">Mature</strong> : Ready for adoption or integration into other standards.</li>
</ul>
<p>The research and development sections are visible during the present development cycle. Deprecated & placeholder sections are hidden when this page loads, but you may toggle the visibility for these sections with the button the top of the table of contents or the button below:</p>
<p><button id="status-filter" data-status-filter="placeholder,deprecated" style="/*padding: 0.5em; font-size: 1.3em; font-weight:700; background: #FF6; border-radius: 0.5em */">Reveal Placeholder & Deprecated Sections</button></p>
</section>
<section id="goals-and-requirements">
<div class="header-wrapper">
<h3 id="x1-3-goals-and-requirements" class="headerPlus3 marker"><bdi class="secno">1.3 </bdi>Goals and Objectives</h3><a class="self-link" href="#goals-and-requirements" aria-label="Permalink for Section 1.3"></a></div>
<p>The goal of the APCA Readability Criterion (ARC) and supporting documents is to make digital products including web, ePub, PDF, applications, mobile apps, and other emerging technologies, more readable, accessible, and usable for all people, including those with visual impairments. This goal will be met through evidence-based science and responding to changing technologies.</p>
<p>Research and development work beginning in early 2019, identified issues with the existing WCAG 2.x contrast success criterion. Correcting these issues shaped the guidelines contained herein.</p>
<p>ARC embodies a much wider scope, and is not confined merely to contrast, but to the entire visual presentation of text and non-text content. The reality is that the very context-sensitive nature of the human vision system requires this more complete, holistic approach to visual perception design guidelines.</p>
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<section id="normative-requirements">
<div class="addition statusStatic floatAddition review"><a href="#section-status-levels" class="status-link"><strong>Review</strong></a></div>
<div class="header-wrapper"><h2 id="x2-normative-requirements" class="headerPlus marker"><bdi class="secno">2. </bdi>NORMATIVE REQUIREMENTS</h2><a class="self-link" href="#normative-requirements" aria-label="Permalink for Section 2."></a></div>
<p class="normative-statement"><em>This section provides requirements which must be followed for <a>conformance</a>, meaning it is <a href="#dfn-normative" class="internalDFN" data-link-type="dfn">normative</a>.</em></p>
<details class="summary">
<summary>Plain language summary of <q>Normative requirements</q></summary>
<p>There are two types of content in this document:</p>
<ul>
<li><strong>Normative:</strong> what you must do to meet the guidelines.</li>
<li><strong>Non-normative:</strong> advice to help you meet the guidelines. This is also called <q>Informative</q>.</li>
</ul>
</details>
<p>In addition to this section, the <a href="#criterion">Visual Presentation</a>, <a href="#visual-contrast">Visual Contrast</a>, <a href="#nontext-contrast-">Nontext Contrast</a>, <a href="#user-integration">User Integration</a>, and <a href="#conformance">Conformance</a> sections in APCA provide <a href="#dfn-normative" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-normative-1">normative</a> content and define requirements that impact conformance claims. Introductory material, appendices, sections marked as <q>non-normative</q>, diagrams, examples, and notes are <a href="#dfn-informative" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-informative-1">informative</a> (non-normative). Non-normative material provides advisory information to help interpret the guidelines but does not create requirements that impact a conformance claim.</p>
<p>The key words <em class="rfc2119" title="MAY"><em class="rfc2119">MAY</em></em>, <em class="rfc2119" title="MUST"><em class="rfc2119">MUST</em></em>, <em class="rfc2119" title="MUST NOT"><em class="rfc2119">MUST NOT</em></em>, <em class="rfc2119" title="NOT RECOMMENDED"><em class="rfc2119">NOT RECOMMENDED</em></em>, <em class="rfc2119" title="RECOMMENDED"><em class="rfc2119">RECOMMENDED</em></em>, <em class="rfc2119" title="SHOULD"><em class="rfc2119">SHOULD</em></em>, and <em class="rfc2119" title="SHOULD NOT"><em class="rfc2119">SHOULD NOT</em></em> are to be interpreted as described in [<cite><a class="bibref" data-link-type="biblio" href="#bib-rfc2119" title="Key words for use in RFCs to Indicate Requirement Levels">RFC2119</a></cite>].</p>
<div class="note" id="issue-container-generatedID-0"><div role="heading" class="ednote-title marker" id="h-ednote-0" aria-level="3"><span class="noteHeading">Development Note</span><a class="self-link" aria-label="§" href="#issue-container-generatedID-0"></a></div><p class="">Objectives and critical errors are normative. Guidelines, test methods, and design guides are informative.</p></div>
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<section id="criterion">
<div class="addition statusStatic floatAddition review"><a href="#section-status-levels" class="status-link"><strong>Review</strong></a></div>
<div class="header-wrapper"><h2 id="x3-criterion" class="headerPlus"><bdi class="secno">3. </bdi>SUMMARY: Visual Presentation</h2><a class="self-link" href="#criterion" aria-label="Permalink for Section 3."></a></div>
<div style="position: relative; margin: 1em auto; padding: 0.3em 0 1em; background:#fed; border: 1px dotted #246c;/*border-color: #aac6 #55d4 #55d4 #aac6 ;*/border-radius:2em;
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<div class="h3 headerPlus2t" style="position: relative; padding: 0; text-align: center; margin: 0 ;">Visual Contrast & Design Guidance<br>
<img src="./img/APCAlogov2bugonly.png" alt="APCA logo" style="position: relative; margin: 0 auto; top:12px; width: 33%;"> <img src="./img/ARCtextPaths_v01.svg" alt="IRT logo" style="position: relative; margin: 0 auto; top:12px; width: 50%;">
</div>
</div>
<p class="normative-statement"><em>This section provides requirements which must be followed for <a>conformance</a>, meaning it is <a href="#dfn-normative" class="internalDFN" data-link-type="dfn">normative</a>.</em></p>
<details class="summary">
<summary>Plain language summary of <q>Guidelines</q></summary>
<ul>
<li>Visual contrast (lightness contrast)</li>
<ul><li>Use Cases (primary content, sub-fluent)</li>
<li>Text contrasts</li>
<li>Font characteristics</li>
</ul>
<li>Color contrast (hue contrast)</li>
<ul><li>Use of color (hue and colorfulness)</li>
<li>Non-text contrasts</li>
<li>Dataviz characteristics</li>
</ul>
<li>User integration</li>
<ul><li>Visual modes (dark, light, dalton) </li>
<li>Visual hierarchy </li>
<li>Interactive (links, forms, navigation) </li>
</ul></ul>
</details>
<hr>
<h2 id="visual-contrast" class="headerPlus2 clb">Visual Contrast</h2>
<h4 class="headerZero4i">Designing for Readability, Understandability, and Accessibility</h4>
<p>This section illuminates the APCA Readability Criterion's comprehensive coverage of visual presentation. Depending on application, ARC is usable as a stand-alone suite for design guidance. While the eventual goal is integration into relevant standards such as ISO, WCAG, or ADA, the current conformance testing as described herein is independent. Further, these guidelines are a living work-in-progress, is in development, and not yet a part of any other final published standard or guideline.</p>
<h4 id="platform" class="headerPlus4">Platforms</h4>
<ul>
<li>All desktop & mobile platforms including, but not limited to, Android, iOS, MacOS, Linux, Windows.</li>
<li>Interactive embedded systems with self-illuminated display technologies, including point-of-sale kiosks, ATMs, parking meters.</li>
<li>Passive public display systems including digital restaurant menus, dynamic billboards, self-illuminated business signage which conveys a message or meaning.</li>
</ul>
<h3 id="medium" class="headerMinus4">Mediums</h3>
<ul>
<li>Web pages and web applications</li>
<li>Visually readable documents including PDF, word processing documents, ePub, and slideware.</li>
<li>Live action and animated, video, film, virtual reality, games, and including menus and controls for interaction.</li>
</ul>
<h4 id="technology" class="headerMinus4">Technologies</h4>
<ul>
<li>Self-illuminated display technologies, including, but not limited to, OLED, back-lit emissive or transmissive LCD, discrete LED, plasma, florescent, CRT, rear-projection, front-projection. </li>
<li>Including form factors for desktop, laptop, tablet, smart phone, VR headset, point-of-sale kiosk, billboards, menus, and other signage.</li>
</ul>
<h4 id="development-environment" class="headerMinus4">Development Environments</h4>
<ul>
<li>Content authoring applications for visually readable content which can specify the font-size & weight, and the text and background colors. </li>
<li>Presentation related coding languages including HTML, CSS, Javascript, Postscript, PHP, Python, etc.</li>
<li>Video editing, titling, color grading, game development, and related temporal authoring systems.</li>
</ul>
<hr>
<h2 id="visual-contrast-map" class="headerPlus2t clb">Visual Contrast</h2>
<h3 class="headerZero4">Guidelines Map</h3>
<ol class="roman">
<li><strong>Text contrasts</strong> • understanding the need for luminance
<ul>
<li>Font characteristics • weight, size, and glyph design</li>
<li>Use Cases • primary content vs sub-fluent vs spot readable</li>
<li>White space • line&letter spacing, element padding</li>
</ul></li>
<li><strong>Non-text contrasts</strong> • semantic and non-semantic elements
<ul>
<li>Use of color (hue and colorfulness) – Hue and colorfulness to augment </li>
<li>Other forms of contrast • shape, size, distance, motion</li>
<li>Dataviz characteristics • unique needs of dataviz</li>
<li>Interactive • links, forms, navigation, and controls</li>
<li>Visual hierarchy • semantic layouts and organizing information</li>
</ul></li>
<li><strong>User integration</strong> • personalization and environment
<ul>
<li>Visual modes • dark, light, dalton, alternate color schemes </li>
<li>Zooming text or view, and text reflow</li>
<li>User adjustable properties and style sheets</li>
<li>Workspace and environmental illumination</li>
<li>Visual fatigue and ocular health</li>
</ul></li>
</ol>
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<section class="criterion" id="visual-contrast-text">
<div class="addition sticky floatAddition development"><a href="#section-status-levels" class="status-link">Section status: <strong>Development</strong></a></div>
<div class="header-wrapper"><h2 id="x4-visual-contrast-text" class="headerPlus"><bdi class="secno">4. </bdi>VISUAL CONTRAST • TEXT</h2><a class="self-link" href="#visual-contrast-text" aria-label="Permalink for Section 4."></a></div>
<p class="normative-statement"><em>This section provides requirements which must be followed for <a>conformance</a>, meaning it is <a href="#dfn-normative" class="internalDFN" data-link-type="dfn">normative</a>.</em></p>
<div class="header-wrapper"><h3 id="x4-1-luminance-contrast" class="headerPlus3"><bdi class="secno">4.1 </bdi>Guideline: Luminance Contrast</h3><a class="self-link" href="#luminance-contrast" aria-label="Permalink for Section 4.1"></a></div>
<p class="">Provide sufficient lightness/darkness contrast between foreground and background.</p>
<details class="categories">
<summary>Functional categories for <q>Lightness contrast between text and background</q></summary>
<p>This objective relates to the following functional categories:</p>
<ul>
<li>Sensory - Light, Contrast</li>
<li>Sensory - Vision, Color</li>
<li>Psychophysical - Discernment, Recognition</li>
<li>Cognitive - Language, Comprehension</li>
<li>Cognitive - Tasks, Instructions</li>
</ul>
</details>
<section>
<h3 id="objective-lightness" class="objective-header"><div>Objective:</div> Ample Lightness Contrast Between Text and Background</h3>
<p style="position: relative; float:right; margin:0; transform: scale(-1, 1);"><img src="./img/ReadingOrangeMan.png" height="240" alt="a little orange man reading a magenta book"id="" /></p>
<p class="objective" status="position: relative; clear: left;">Provides adequate luminance contrast (lightness/darkness difference) between background and text or non-text colors in order to read the text easily, or discern non-text meaning and function easily.</p>
<p>Set the lightness contrast as appropriate for a font family, font weight, x-height, and the use-case of the text.</p>
<ul>
<li>Font weight has a substantial effect on visual contrast</li>
<li>Font size substantially affects readability for various acuity impairments</li>
<li>All sighted users require ample lightness/darkness contrast for best readability</li>
</ul>
<h3 id="objective-" class="objective-header"><div>Objective:</div> Multiple User Selectable Modes or Color Schemes</h3>
<p style="position: relative; float:right; margin:0; transform: scale(-1, 1);"><img src="./img/matrix-1013612gradeSMALL.png" height="240" alt="Matrix of cubes"id="" /></p>
<p class="objective" status="position: relative; clear: left;">Provides at a minimum a light mode and a dark mode, switchable using the <code>prefers-color-scheme</code> media query.</p>
<p>Create two or more color schemes using the visual contrast conformance specifications, and allow switching between them by the user, either through the use of media queries, or through the use of a user interface, such as radio buttons in the header.</p>
<ul>
<li>Some users need a dark mode while others prefer a light mode.</li>
<li>Other possible modes include low contrast, high contrast, and Daltonization.</li>
</ul>
<h3 id="objective-" class="objective-header"><div>Objective:</div> Reduce glare and eye fatigue when reading columns of body text.</h3>
<p style="position: relative; float:right; margin:0; transform: scale(-1, 1);"><img src="./img/readpaperSMALL.png" height="240" alt="a little yellow man reading a paper while sitting at a table with a cup of coffee" id="" /></p>
<p class="objective" status="position: relative; clear: left;"> Use psychophysical design techniques to anchor the adaptation point above the text background to prevent eye fatigue or strain from excess luminance. </p>
<p>As an example, in the document you are reading right now, there is a white border around the text background, and this background is at a reduced luminance. The white border anchors the adaptation state, and the reduced luminance behind this text is closer to the equivalent of reading dark text printed on diffuse, light paper.</p>
<ul>
<li>Excess luminance can be a problem for all users, depending on certain factors.</li>
<li>Long periods of focused reading requires an optimum luminance that is neither too dim nor too bright.</li>
<li>In order to facilitate this, the adaptation state needs to be controlled with something to anchor it at a position that is brighter than the text area.</li>
</ul>
<hr class="abstract">
<h2 class="tests-header">Testing Criterion, Conformance, and Methods</h2>
<ul class="tests-list">
<li><a class="tests-link" href="./tests/visual-readability-contrast/">Visual Readability Contrast Test Methods.</a><br>Here are the technical details for the readability criterion, in terms of conformance, testing, techniques, and resources relating to setting the lightness contrast as appropriate for a font family, font weight, and x-height. (CSS)</li>
<li><a class="tests-link" href="./tests/bronze-simple-mode/">Bronze Simple Mode Contrast Test Methods.</a><br>Simple mode is a more basic way to conform a website for readability. Intended as an easier point of entry to APCA methods and guidelines.</li>
<li><a class="tests-link" href="./tests/multi-mode/">Multiple Color Scheme Contrast Test Methods.</a><br>Technical details for implementing user selectable, multiple color schemes and multiple contrast modes.</li>
</ul>
<hr>
<h2 class="guide-header">Helpful Planning & Design Guides</h2>
<ul class="guide-list">
<li><a class="guide-link" href="./guides/designing-with-visual-contrast/">Designing With Visual Contrast <span>How-To Guide</span></a><br>Here are guides for planning, designing, and implementing accessible visual contrast in your content. Different guides for different audiences from a bird's-eye-view, to more design oriented. </li>
<li><a class="guide-link" href="./guides/paper-reading-experience/">Designing for the Paper Reading Experience</a><br> the paper reading experience is a helpful set of design considerations for reducing eyestrain and eye fatigue.</li>
</ul>
</section>
<div class="note" id="issue-container-generatedID-2">
<div role="heading" class="ednote-title marker" id="h-ednote-2" aria-level="4"><span class="noteHeading">Development Note</span><a class="self-link" aria-label="§" href="#issue-container-generatedID-2"></a></div>
<div class="">
<p>Visual Contrast is a paradigm shift from WCAG 2.x contrast in terms of methodology and scope:</p>
<ul>
<li>New contrast calculations based on modern research into visual perception and visual reading, provide a perceptually uniform result which extends the useable range allowing for automated color selection and calculating for special modes such as dark mode.</li>
<li>Revising and merging the 1.4.x criteria into fewer and more comprehensive guidelines.</li>
<li>New tests for text and non-text contrast that consider important spatial effects. </li>
</ul>
<p>This is a significant change from the WCAG 2.x <q>1.4.3 Contrast (Minimum)</q> and <q>1.4.6 Contrast (Enhanced)</q>. The reason for this change is that the understanding of contrast has matured and the available research and body of knowledge has made breakthroughs in advancing the understanding of <q>visual contrast</q>.</p>
<p>This new guidance more accurately models human visual perception of contrast of high spatial frequency stimuli, such as text and non-text elements, presented on self-illuminated displays. </p>
<p>The goal is to improve understanding of the functional needs of all users, and more effectively match the needs of those who face barriers accessing content. This new perception-based model is more context dependent than a strict light-ratio measurement.</p>
<p>This model is more responsive to user needs and allows designers more choice in visual presentation. It does this by including multi-factor assessment tests which integrate contrast with inter-related elements of visual readability, such as font features. It includes tests to determine an upper limit of contrast, where elevated contrast may impact usability.</p>
</div>