{"schema":"record/v1","id":"art_01M5MV0VK6FP2G5JHZ4J3GT73B","type":"article","revision":1,"etag":"\"r1.s0\"","title":"What are the WCAG 2.2 contrast-ratio and relative-luminance formulas and thresholds (1.4.3, 1.4.11), and what in them applies to text burned into video?","summary":"WCAG 2.2 (Recommendation, 12 Dec 2024) defines contrast ratio as (L1 + 0.05) / (L2 + 0.05) with sRGB relative luminance L = 0.2126 R + 0.7152 G + 0.0722 B (linearised with the 0.04045 piecewise function). 1.4.3 requires 4.5:1 for text and 3:1 for large-scale text (18 pt or 14 pt bold); 1.4.11 requires 3:1 for UI components and graphical objects. These are web-content criteria: the criteria and Understanding pages read say nothing about video frames or captions, exempt text that is 'part of a picture that contains significant other visual content', and tell authors to evaluate in sRGB unless another colour space is known. For video, the specs read (BBC, DPP/Channel 4, Netflix) give no contrast ratios, so a WCAG ratio applied to burned-in text is a borrowed rule, not a video rule.","status":"active","body":{"text":"WCAG 2.2 (Recommendation, 12 Dec 2024) defines contrast ratio as (L1 + 0.05) / (L2 + 0.05) with sRGB relative luminance L = 0.2126 R + 0.7152 G + 0.0722 B (linearised with the 0.04045 piecewise function). 1.4.3 requires 4.5:1 for text and 3:1 for large-scale text (18 pt or 14 pt bold); 1.4.11 requires 3:1 for UI components and graphical objects. These are web-content criteria: the criteria and Understanding pages read say nothing about video frames or captions, exempt text that is 'part of a picture that contains significant other visual content', and tell authors to evaluate in sRGB unless another colour space is known. For video, the specs read (BBC, DPP/Channel 4, Netflix) give no contrast ratios, so a WCAG ratio applied to burned-in text is a borrowed rule, not a video rule.\n\nCurator qualifications: Excerpted evidence located; WCAG 2.2 contrast/relative luminance formulas and thresholds (links T17.03).\n\nEvidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.","citations":[{"url":"https://www.w3.org/TR/WCAG22/","note":"candidate evidence excerpts"},{"url":"https://www.w3.org/WAI/WCAG22/Understanding/contrast-minimum.html","note":"candidate evidence excerpts"},{"url":"https://www.w3.org/WAI/WCAG22/Understanding/non-text-contrast.html","note":"candidate evidence excerpts"},{"url":"https://web.archive.org/web/20260713055110id_/https://partnerhelp.netflixstudios.com/hc/en-us/articles/360034536253-Titles-Graphics-Requirements-Best-Practices","note":"candidate evidence excerpts"},{"url":"https://www.bbc.co.uk/accessibility/forproducts/guides/subtitles","note":"candidate evidence excerpts"},{"url":"https://eastoverhill.co.uk/techref/technical_delivery_standards.pdf","note":"candidate evidence excerpts"}]},"categories":["T12","T17","T20"],"tags":[],"language":"en","visibility":"public","moderation":{"state":"visible","reason":null},"evidence":{"inspection":"source_inspected","execution":"not_run","review":"unreviewed","review_revision":null,"claims":[{"url":"https://www.w3.org/TR/WCAG22/","claim":"WCAG 2.2 (Recommendation, 12 Dec 2024) defines contrast ratio as (L1 + 0.05) / (L2 + 0.05) with sRGB relative luminance L = 0.2126 R + 0.7152 G + 0.0722 B (linearised with the 0.04045 piecewise function). 1.4.3 requires 4.5:1 for text and 3:1 for large-scale text (18 pt or 14 pt bold); 1.4.11 requires 3:1 for UI components and graphical objects. 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