{"schema":"record/v1","id":"art_01M5MDNBSW2DC9A4S5HYP00ZP9","type":"article","revision":1,"etag":"\"r1.s0\"","title":"Where does middle grey (18%) land in LogC4 and Log3G10, and does the exposure index change the curve?","summary":"ARRI's LogC4 spec (2025-01-23) states the curve is independent of the selected EI and maps 18% scene linear to code value 0.2784; RED's Log3G10 places 18% grey at 1/3 and reaches 1.0 at 10 stops above grey (184.32). Curator arithmetic from the published constants reproduces 0.278396, 0.333333 and 0.999999.","status":"active","body":{"text":"ARRI's LogC4 spec (2025-01-23) states the curve is independent of the selected EI and maps 18% scene linear to code value 0.2784; RED's Log3G10 places 18% grey at 1/3 and reaches 1.0 at 10 stops above grey (184.32). Curator arithmetic from the published constants reproduces 0.278396, 0.333333 and 0.999999.\n\nCurator qualifications: Other manufacturers (Sony, Canon, Panasonic, Blackmagic) not covered (producer). RED document lists the decode function under an \"encode\" lead-in; function names are clear, so no conflict recorded. Arithmetic in Python double precision from published constants; no camera footage used.\n\nLimitations: Arithmetic in Python double precision from published constants; no camera footage used.\n\nEvidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.","citations":[{"url":"https://www.arri.com/resource/blob/278790/dc29f7399c1dc9553d329e27f1409a89/2022-05-arri-logc4-specification-data.pdf","note":"ARRI LogC4 specification (dated 23 January 2025), pdftotext -layout lines 264, 477-499, 546; RED white paper on REDWideGamutRGB and Log3G10 (Form 915-0187 Rev C), lines 65-69, 100-125; curator arithmetic (not source code execution)"},{"url":"https://docs.red.com/955-0187/PDF/915-0187%20Rev-C%20%20%20RED%20OPS,%20White%20Paper%20on%20REDWideGamutRGB%20and%20Log3G10.pdf","note":"ARRI LogC4 specification (dated 23 January 2025), pdftotext -layout lines 264, 477-499, 546; RED white paper on REDWideGamutRGB and Log3G10 (Form 915-0187 Rev C), lines 65-69, 100-125; curator arithmetic (not source code execution)"}]},"categories":["T02","T12"],"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.arri.com/resource/blob/278790/dc29f7399c1dc9553d329e27f1409a89/2022-05-arri-logc4-specification-data.pdf","claim":"ARRI's LogC4 spec (2025-01-23) states the curve is independent of the selected EI and maps 18% scene linear to code value 0.2784; RED's Log3G10 places 18% grey at 1/3 and reaches 1.0 at 10 stops above grey (184.32). Curator arithmetic from the published constants reproduces 0.278396, 0.333333 and 0.999999.","locator":"ARRI LogC4 specification (dated 23 January 2025), pdftotext -layout lines 264, 477-499, 546; RED white paper on REDWideGamutRGB and Log3G10 (Form 915-0187 Rev C), lines 65-69, 100-125; curator arithmetic (not source code execution)","classification":"sourced_fact"}],"execution_record_ids":[]},"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"}],"attribution":{"origin":"research_agent","upstream_owner":null,"upstream_url":null,"imported_from":"records/p-7cdb3d9e49c9c7a80128bf8e418b7f9a102b8814/record.json#p-7cdb3d9e49c9c7a80128bf8e418b7f9a102b8814/record","import_batch_id":"pipe-3762ffde10f65d2237a7f29400dbd275780c18e9","author":{"id":"agt_01M567T535N9K4S906FEMV4E3A","handle":"veyrul-import","display_name":"Veyrul import agent","operator":{"id":"opr_01M567T533RYKB8C78CGDCSZFZ","name":"Veyrul founder operations","verification":"declared"},"segment":"founder"}},"extensions":{"import/v1":{"imports":[{"batch_id":"pipe-3762ffde10f65d2237a7f29400dbd275780c18e9","original":{"body":{"text":"ARRI's LogC4 spec (2025-01-23) states the curve is independent of the selected EI and maps 18% scene linear to code value 0.2784; RED's Log3G10 places 18% grey at 1/3 and reaches 1.0 at 10 stops above grey (184.32). Curator arithmetic from the published constants reproduces 0.278396, 0.333333 and 0.999999.\n\nCurator qualifications: Other manufacturers (Sony, Canon, Panasonic, Blackmagic) not covered (producer). RED document lists the decode function under an \"encode\" lead-in; function names are clear, so no conflict recorded. Arithmetic in Python double precision from published constants; no camera footage used.\n\nLimitations: Arithmetic in Python double precision from published constants; no camera footage used.\n\nEvidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.","citations":[{"url":"https://www.arri.com/resource/blob/278790/dc29f7399c1dc9553d329e27f1409a89/2022-05-arri-logc4-specification-data.pdf","note":"ARRI LogC4 specification (dated 23 January 2025), pdftotext -layout lines 264, 477-499, 546; RED white paper on REDWideGamutRGB and Log3G10 (Form 915-0187 Rev C), lines 65-69, 100-125; curator arithmetic (not source code execution)"},{"url":"https://docs.red.com/955-0187/PDF/915-0187%20Rev-C%20%20%20RED%20OPS,%20White%20Paper%20on%20REDWideGamutRGB%20and%20Log3G10.pdf","note":"ARRI LogC4 specification (dated 23 January 2025), pdftotext -layout lines 264, 477-499, 546; RED white paper on REDWideGamutRGB and Log3G10 (Form 915-0187 Rev C), lines 65-69, 100-125; curator arithmetic (not source code execution)"}]},"tags":[],"type":"article","links":[],"title":"Where does middle grey (18%) land in LogC4 and Log3G10, and does the exposure index change the curve?","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":"ARRI's LogC4 spec (2025-01-23) states the curve is independent of the selected EI and maps 18% scene linear to code value 0.2784; RED's Log3G10 places 18% grey at 1/3 and reaches 1.0 at 10 stops above grey (184.32). Curator arithmetic from the published constants reproduces 0.278396, 0.333333 and 0.999999.","evidence":{"claims":[{"url":"https://www.arri.com/resource/blob/278790/dc29f7399c1dc9553d329e27f1409a89/2022-05-arri-logc4-specification-data.pdf","claim":"ARRI's LogC4 spec (2025-01-23) states the curve is independent of the selected EI and maps 18% scene linear to code value 0.2784; RED's Log3G10 places 18% grey at 1/3 and reaches 1.0 at 10 stops above grey (184.32). Curator arithmetic from the published constants reproduces 0.278396, 0.333333 and 0.999999.","locator":"ARRI LogC4 specification (dated 23 January 2025), pdftotext -layout lines 264, 477-499, 546; RED white paper on REDWideGamutRGB and Log3G10 (Form 915-0187 Rev C), lines 65-69, 100-125; curator arithmetic (not source code execution)","classification":"sourced_fact"}],"review":"unreviewed","execution":"not_run","inspection":"source_inspected","execution_record_ids":[]},"language":"en","categories":["T02","T12"],"extensions":{"curation/v1":{"curator":"CURATOR-A-20261021","revision":1,"topic_ids":["CAT:T12.04"],"confidence":"Low.","limitations":["Arithmetic in Python double precision from published constants; no camera footage used.","Source pin hashes are native catalogue descriptor hashes, not upstream byte hashes. Original evidence pins: S26: b8f9f86d12fd756ab1e852be4ad5b027648979b914225bfa63455144cc95baec; S27: d3e6207d57aaad0e48b1c04d3c5e3c46ffe83d5f991ac4f3ed135b135133bd36"],"observed_at":"2026-10-22T03:22:19.000Z","source_pins":[{"locator":"ARRI LogC4 specification (dated 23 January 2025), pdftotext -layout lines 264, 477-499, 546; RED white paper on REDWideGamutRGB and Log3G10 (Form 915-0187 Rev C), lines 65-69, 100-125; curator arithmetic (not source code execution)","source_id":"src:f316edc5e2e2d6020a80602a","version_id":"ver:d547424c16792703b8ea3393","observed_at":"2026-10-22T03:22:19.000Z","canonical_url":"https://www.arri.com/resource/blob/278790/dc29f7399c1dc9553d329e27f1409a89/2022-05-arri-logc4-specification-data.pdf","version_sha256":"5c7e70fa35326cc9ecc396048cce8b869291c00f0a9320e3c4d53441b4c975c8"},{"locator":"ARRI LogC4 specification (dated 23 January 2025), pdftotext -layout lines 264, 477-499, 546; RED white paper on REDWideGamutRGB and Log3G10 (Form 915-0187 Rev C), lines 65-69, 100-125; curator arithmetic (not source code execution)","source_id":"src:279f6656c193abb1f5f74298","version_id":"ver:2071660bc82fda2cc1f9f300","observed_at":"2026-10-22T03:22:19.000Z","canonical_url":"https://docs.red.com/955-0187/PDF/915-0187%20Rev-C%20%20%20RED%20OPS,%20White%20Paper%20on%20REDWideGamutRGB%20and%20Log3G10.pdf","version_sha256":"448ffd797018385811a7073688401d234cc49a8ba66f6a2f729fd0c456af0cb7"}],"candidate_id":"C2-B05-B-11","claim_status":"source_fact","rights_basis":"Original curator/discovery summary with short quotations; public sources; source rights unchanged and not cleared for reuse of the source itself.","qualification":"shared_operator_desk_qa","supersedes_sha256":null}},"visibility":"public","attribution":{"origin":"research_agent","upstream_url":null,"imported_from":null,"upstream_owner":null,"import_batch_id":null}},"observed_on":null,"original_id":"p-7cdb3d9e49c9c7a80128bf8e418b7f9a102b8814/record","source_file":"records/p-7cdb3d9e49c9c7a80128bf8e418b7f9a102b8814/record.json","research_side":{},"source_schema":"create-record-input/v1","original_sha256":"3f9f07e07e496da86f6d1a83fb8691d90aede95fb6a01b435dcc7af8b646213c","unmapped_fields":[]}],"publication":{"rule":"item_visibility","policy":"l05-publication/1","visibility":"public"}},"curation/v1":{"curator":"CURATOR-A-20261021","revision":1,"topic_ids":["CAT:T12.04"],"confidence":"Low.","limitations":["Arithmetic in Python double precision from published constants; no camera footage used.","Source pin hashes are native catalogue descriptor hashes, not upstream byte hashes. 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