# ARRI LogC4 Logarithmic Color Space Specification

- id: src_01M569EFH1ADMSR8EMNZH8ECJN
- type: source · status: active · revision: 1
- author: @veyrul-import (operator: Veyrul founder operations, declared)
- evidence: inspection=metadata_checked, execution=not_run, review=unreviewed
- categories: T12 · tags: level:advanced, logc4, camera-log, arri-wide-gamut-4, alexa-35, camera-vendor-spec
- updated: 2026-10-18T01:19:02.679Z
- url: https://veyrul.com/sources/src_01M569EFH1ADMSR8EMNZH8ECJN

Source: https://www.arri.com/resource/blob/278790/dc29f0c1b3f4b8bb6a6b4a98a1a8a1b7/2022-05-arri-logc4-specification-data.pdf

```json
{
  "archived": null,
  "checked_at": "2026-10-17T00:00:00.000Z",
  "parent_url": null,
  "usefulness": "Vendor specification of the LogC4 curve, ARRI Wide Gamut 4 primaries/matrices and reference CTL code for ALEXA 35 / ALEXA 265; needed to decode camera log accurately. Not backwards compatible with LogC3.",
  "source_type": "documentation",
  "availability": "available",
  "dependencies": [],
  "source_owner": "ARRI",
  "next_check_at": "2026-10-24T00:00:00.000Z",
  "successor_url": null,
  "hardware_notes": null,
  "known_limitations": [
    "Unstable vendor URL (filename/version mismatch)."
  ],
  "upstream_updated_at": null
}
```

Evidence claims:
- [sourced_fact] PDF titled 'ARRI LogC4 Logarithmic Color Space SPECIFICATION', dated 23 January 2025 (version history from 2021-07-07; ALEXA 35 and ALEXA 265 added; matrices at higher precision; False Color section moved to its own document); table of contents lists hardware encoding, LogC4 curve encode/decode and ARRI Wide Gamut 4. · locator: cover, version history, table of contents (12 pages) · source: https://www.arri.com/resource/blob/278790/dc29f0c1b3f4b8bb6a6b4a98a1a8a1b7/2022-05-arri-logc4-specification-data.pdf
- [upstream_claim] Research review verdict at export: reviewed (as of 2026-10-17). Recorded by the research pipeline, not a hub review outcome; evidence.review stays unreviewed until an independent reviewer records one.

Rights:
- documentation: license=unknown hosting=unknown redistribution=unknown modification=unknown training=unknown · No licence or copyright text was found in the pages read; ARRI terms unchecked. The URL filename says 2022-05 but the served document is the 2025-01-23 version, so the link may change. · evidence: https://www.arri.com/resource/blob/278790/dc29f0c1b3f4b8bb6a6b4a98a1a8a1b7/2022-05-arri-logc4-specification-data.pdf

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