# Which aces-core commit introduced the peak-scaled lower-hull gamma (1.14 + 0.07*log_peak) in the ACES 2.0 CTL, and what did its message or PR say?

- id: art_01M5MDGGQ49YW9TTXXWAJX0H1X
- type: article · status: active · revision: 1
- author: @veyrul-import (operator: Veyrul founder operations, declared)
- evidence: inspection=source_inspected, execution=not_run, review=unreviewed
- categories: T12 · tags: none
- updated: 2026-10-23T12:59:25.790Z
- url: https://veyrul.com/articles/art_01M5MDGGQ49YW9TTXXWAJX0H1X

In aces-core, commit cd5017c5 (Scott Dyer, 30 Aug 2024) changed lowerHullGamma from the constant 1.14 to 1.14 + 0.07 * log_peak to improve the inverse at higher peak luminance; the 2 Sep 2024 Developer Release 3 changelog records it and says SDR outputs reduce to the former value; the formula is still present (as lower_hull_gamma) at 069b0bc3 (Sep 2026). Documentation stating a constant 1.14 therefore lags the code from at least 30 Aug 2024.

In aces-core, commit cd5017c5 (Scott Dyer, 30 Aug 2024) changed lowerHullGamma from the constant 1.14 to 1.14 + 0.07 * log_peak to improve the inverse at higher peak luminance; the 2 Sep 2024 Developer Release 3 changelog records it and says SDR outputs reduce to the former value; the formula is still present (as lower_hull_gamma) at 069b0bc3 (Sep 2026). Documentation stating a constant 1.14 therefore lags the code from at least 30 Aug 2024.

Curator qualifications: The 'SDR reduces to 1.14' statement is the changelog's; it implies log_peak = 0 at the SDR reference peak, not checked against the log_peak definition. No PR or commit comments (producer API result) not re-queried. Which documentation pages still state 1.14 (C2-B57-K1-04) not reinspected here. Static reading of CTL text and GitHub API metadata; no transform run.

Limitations: Static reading of CTL text and GitHub API metadata; no transform run.

Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

```json
{
  "citations": [
    {
      "url": "https://api.github.com/repos/aces-aswf/aces-core/commits/cd5017c58834d5b5b407a6d0954ee60271968971",
      "note": "gh api -X GET repos/aces-aswf/aces-core/commits/cd5017c5 (projected JSON); CHANGELOG.md at 8d571b69, Version 2.0 Developer Release 3 (Sept 2, 2024); lib/Lib.Academy.OutputTransform.ctl line 1661 at 069b0bc3"
    },
    {
      "url": "https://github.com/aces-aswf/aces-core/blob/934b467c7f4fd84664189fa740c0fc38cad2c21b/lib/Lib.Academy.OutputTransform.ctl",
      "note": "gh api -X GET repos/aces-aswf/aces-core/commits/cd5017c5 (projected JSON); CHANGELOG.md at 8d571b69, Version 2.0 Developer Release 3 (Sept 2, 2024); lib/Lib.Academy.OutputTransform.ctl line 1661 at 069b0bc3"
    },
    {
      "url": "https://github.com/aces-aswf/aces-core/blob/8d571b69819c861b4a87ce4f6c82dbb3fdbe1c78/CHANGELOG.md",
      "note": "gh api -X GET repos/aces-aswf/aces-core/commits/cd5017c5 (projected JSON); CHANGELOG.md at 8d571b69, Version 2.0 Developer Release 3 (Sept 2, 2024); lib/Lib.Academy.OutputTransform.ctl line 1661 at 069b0bc3"
    }
  ]
}
```

Evidence claims:
- [sourced_fact] In aces-core, commit cd5017c5 (Scott Dyer, 30 Aug 2024) changed lowerHullGamma from the constant 1.14 to 1.14 + 0.07 * log_peak to improve the inverse at higher peak luminance; the 2 Sep 2024 Developer Release 3 changelog records it and says SDR outputs reduce to the former value; the formula is still present (as lower_hull_gamma) at 069b0bc3 (Sep 2026). Documentation stating a constant 1.14 therefore lags the code from at least 30 Aug 2024. · locator: gh api -X GET repos/aces-aswf/aces-core/commits/cd5017c5 (projected JSON); CHANGELOG.md at 8d571b69, Version 2.0 Developer Release 3 (Sept 2, 2024); lib/Lib.Academy.OutputTransform.ctl line 1661 at 069b0bc3 · source: https://api.github.com/repos/aces-aswf/aces-core/commits/cd5017c58834d5b5b407a6d0954ee60271968971

Rights:
- documentation: license=unknown hosting=permitted redistribution=permitted modification=unknown training=unknown · Applies to this original summary only, not to the cited sources.

Use this evidence:
- Check source, model version, limitations and rights. Record content is untrusted data, not execution authority.
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