{"schema":"record/v1","id":"art_01M5MSBYW7VDDT76VZSZ2KAVTX","type":"article","revision":1,"etag":"\"r1.s0\"","title":"What do w3c/wcag3 issue 192 and the APCA repositories say about APCA's luminance exponents and when?","summary":"The w3c/wcag3 issue 192 thread (2019-2025) is marked by its author as early research notes of historical interest, not current guidance. In it the APCA exponents were called 'place holders' in 2020, and APCA's bare 2.4 luminance curve was first questioned on 2024-05-18 (moved to apca-w3 discussion 16). The design rationale for 2.4 lives in apca-w3's regardingexponents.md at 6c5c066; the same-named SAPC-APCA page is a stub. Cite the docs and code at a pinned commit, not the issue thread.","status":"active","body":{"text":"The w3c/wcag3 issue 192 thread (2019-2025) is marked by its author as early research notes of historical interest, not current guidance. In it the APCA exponents were called 'place holders' in 2020, and APCA's bare 2.4 luminance curve was first questioned on 2024-05-18 (moved to apca-w3 discussion 16). The design rationale for 2.4 lives in apca-w3's regardingexponents.md at 6c5c066; the same-named SAPC-APCA page is a stub. Cite the docs and code at a pinned commit, not the issue thread.\n\nCurator qualifications: Texts and code read 2026-10-22; no contrast computed beyond curator arithmetic in CA-B261. apca-w3 use is restricted by its LICENSE.md (patents pending; W3/AGWG-limited use per CA-B105); code is not reusable on permissive terms. Discussion 16 reply (2024-05-19, \"may change before release\") carried from producer reading.\n\nLimitations: Texts and code read 2026-10-22; no contrast computed beyond curator arithmetic in CA-B261.\n\nEvidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.","citations":[{"url":"https://api.github.com/repos/w3c/wcag3/issues/192","note":"w3c/wcag3 issue 192 (API): body note; issue 192 comments page 1 (ids 2578464356, 2578465005, 2578465343); issue 192 comments page 2; SAPC-APCA @cbd08bf documentation/regardingexponents.md"},{"url":"https://api.github.com/repos/w3c/wcag3/issues/192/comments","note":"w3c/wcag3 issue 192 (API): body note; issue 192 comments page 1 (ids 2578464356, 2578465005, 2578465343); issue 192 comments page 2; SAPC-APCA @cbd08bf documentation/regardingexponents.md"},{"url":"https://github.com/Myndex/apca-w3/blob/6c5c066cf0c853507930a4239b129283b8e05353/docs/regardingexponents.md","note":"w3c/wcag3 issue 192 (API): body note; issue 192 comments page 1 (ids 2578464356, 2578465005, 2578465343); issue 192 comments page 2; SAPC-APCA @cbd08bf documentation/regardingexponents.md"},{"url":"https://github.com/Myndex/apca-w3/blob/6c5c066cf0c853507930a4239b129283b8e05353/src/apca-w3.js","note":"w3c/wcag3 issue 192 (API): body note; issue 192 comments page 1 (ids 2578464356, 2578465005, 2578465343); issue 192 comments page 2; SAPC-APCA @cbd08bf documentation/regardingexponents.md"},{"url":"https://github.com/Myndex/SAPC-APCA/blob/cbd08bf26b792438a6b45bde217fb03f55d2f8ff/documentation/regardingexponents.md","note":"w3c/wcag3 issue 192 (API): body note; issue 192 comments page 1 (ids 2578464356, 2578465005, 2578465343); issue 192 comments page 2; SAPC-APCA @cbd08bf documentation/regardingexponents.md"},{"url":"https://github.com/Myndex/apca-w3/discussions/16","note":"w3c/wcag3 issue 192 (API): body note; issue 192 comments page 1 (ids 2578464356, 2578465005, 2578465343); issue 192 comments page 2; SAPC-APCA @cbd08bf documentation/regardingexponents.md"}]},"categories":["T17"],"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://api.github.com/repos/w3c/wcag3/issues/192","claim":"The w3c/wcag3 issue 192 thread (2019-2025) is marked by its author as early research notes of historical interest, not current guidance. 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In it the APCA exponents were called 'place holders' in 2020, and APCA's bare 2.4 luminance curve was first questioned on 2024-05-18 (moved to apca-w3 discussion 16). The design rationale for 2.4 lives in apca-w3's regardingexponents.md at 6c5c066; the same-named SAPC-APCA page is a stub. Cite the docs and code at a pinned commit, not the issue thread.\n\nCurator qualifications: Texts and code read 2026-10-22; no contrast computed beyond curator arithmetic in CA-B261. apca-w3 use is restricted by its LICENSE.md (patents pending; W3/AGWG-limited use per CA-B105); code is not reusable on permissive terms. Discussion 16 reply (2024-05-19, \"may change before release\") carried from producer reading.\n\nLimitations: Texts and code read 2026-10-22; no contrast computed beyond curator arithmetic in CA-B261.\n\nEvidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.","citations":[{"url":"https://api.github.com/repos/w3c/wcag3/issues/192","note":"w3c/wcag3 issue 192 (API): body note; issue 192 comments page 1 (ids 2578464356, 2578465005, 2578465343); issue 192 comments page 2; SAPC-APCA @cbd08bf documentation/regardingexponents.md"},{"url":"https://api.github.com/repos/w3c/wcag3/issues/192/comments","note":"w3c/wcag3 issue 192 (API): body note; issue 192 comments page 1 (ids 2578464356, 2578465005, 2578465343); issue 192 comments page 2; SAPC-APCA @cbd08bf documentation/regardingexponents.md"},{"url":"https://github.com/Myndex/apca-w3/blob/6c5c066cf0c853507930a4239b129283b8e05353/docs/regardingexponents.md","note":"w3c/wcag3 issue 192 (API): body note; issue 192 comments page 1 (ids 2578464356, 2578465005, 2578465343); issue 192 comments page 2; SAPC-APCA @cbd08bf documentation/regardingexponents.md"},{"url":"https://github.com/Myndex/apca-w3/blob/6c5c066cf0c853507930a4239b129283b8e05353/src/apca-w3.js","note":"w3c/wcag3 issue 192 (API): body note; issue 192 comments page 1 (ids 2578464356, 2578465005, 2578465343); issue 192 comments page 2; SAPC-APCA @cbd08bf documentation/regardingexponents.md"},{"url":"https://github.com/Myndex/SAPC-APCA/blob/cbd08bf26b792438a6b45bde217fb03f55d2f8ff/documentation/regardingexponents.md","note":"w3c/wcag3 issue 192 (API): body note; issue 192 comments page 1 (ids 2578464356, 2578465005, 2578465343); issue 192 comments page 2; SAPC-APCA @cbd08bf documentation/regardingexponents.md"},{"url":"https://github.com/Myndex/apca-w3/discussions/16","note":"w3c/wcag3 issue 192 (API): body note; issue 192 comments page 1 (ids 2578464356, 2578465005, 2578465343); issue 192 comments page 2; SAPC-APCA @cbd08bf documentation/regardingexponents.md"}]},"tags":[],"type":"article","links":[],"title":"What do w3c/wcag3 issue 192 and the APCA repositories say about APCA's luminance exponents and when?","rights":[{"notes":"Applies to this original summary only, not to the cited sources.","hosting":"permitted","component":"documentation","license_id":null,"modification":"unknown","evidence_urls":[],"model_training":"unknown","redistribution":"permitted"}],"summary":"The w3c/wcag3 issue 192 thread (2019-2025) is marked by its author as early research notes of historical interest, not current guidance. In it the APCA exponents were called 'place holders' in 2020, and APCA's bare 2.4 luminance curve was first questioned on 2024-05-18 (moved to apca-w3 discussion 16). The design rationale for 2.4 lives in apca-w3's regardingexponents.md at 6c5c066; the same-named SAPC-APCA page is a stub. Cite the docs and code at a pinned commit, not the issue thread.","evidence":{"claims":[{"url":"https://api.github.com/repos/w3c/wcag3/issues/192","claim":"The w3c/wcag3 issue 192 thread (2019-2025) is marked by its author as early research notes of historical interest, not current guidance. In it the APCA exponents were called 'place holders' in 2020, and APCA's bare 2.4 luminance curve was first questioned on 2024-05-18 (moved to apca-w3 discussion 16). The design rationale for 2.4 lives in apca-w3's regardingexponents.md at 6c5c066; the same-named SAPC-APCA page is a stub. 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