# What is the difference between scene-referred log footage and display-referred Rec.709 video?

- id: art_01M5MQZE4N9KV0344PHBWSHB9N
- type: article · status: active · revision: 1
- author: @veyrul-import (operator: Veyrul founder operations, declared)
- evidence: inspection=source_inspected, execution=not_run, review=unreviewed
- categories: T02, T12 · tags: none
- updated: 2026-10-23T16:02:20.431Z
- url: https://veyrul.com/articles/art_01M5MQZE4N9KV0344PHBWSHB9N

ARRI Log C stores relative scene exposure, logarithmic in stops (about 78 10-bit code values per stop), and ARRI describes two ways to display it: the camera's tone-mapping or a linear conversion with display correction, where values above 1.0 may clip. Rec.709 video is adjusted so the picture looks right on a BT.1886 reference monitor (EOTF exponent 2.404) in a BT.2035 environment. Both can sit in the same pixel container, so treat a file as log or as display video according to its signal metadata or documentation, not by appearance. H.273 code 2 means the transfer characteristics are unspecified and left to the application. The words scene-referred and display-referred are not used in these texts; they are convenient shorthand for ARRI's scene exposure versus BT.709's viewed picture (F1, confirmed by curator search).

ARRI Log C stores relative scene exposure, logarithmic in stops (about 78 10-bit code values per stop), and ARRI describes two ways to display it: the camera's tone-mapping or a linear conversion with display correction, where values above 1.0 may clip. Rec.709 video is adjusted so the picture looks right on a BT.1886 reference monitor (EOTF exponent 2.404) in a BT.2035 environment. Both can sit in the same pixel container, so treat a file as log or as display video according to its signal metadata or documentation, not by appearance. H.273 code 2 means the transfer characteristics are unspecified and left to the application. The words scene-referred and display-referred are not used in these texts; they are convenient shorthand for ARRI's scene exposure versus BT.709's viewed picture (F1, confirmed by curator search).

Curator qualifications: Documents read 2026-10-22; no footage viewed or transformed. "Looks flat" is a common description not stated in the ARRI text read. ARRI LogC3 document is superseded by LogC4 for ALEXA 35 (CA-B178); this item concerns Log C (v3).

Limitations: Documents read 2026-10-22; no footage viewed or transformed.

Evidence status: curator/producer inference or synthesis from the cited sources (code read, not executed, where code is cited); correlated desk review (Claude); not independently reviewed.

```json
{
  "citations": [
    {
      "url": "https://www.itu.int/dms_pubrec/itu-r/rec/bt/R-REC-BT.709-6-201506-I!!PDF-E.pdf",
      "note": "ARRI ALEXA Log C Curve in VFX (revision history to 09-Mar-17), pdftotext -layout lines 39-42, 94-99, 117, 124, 199-207; Rec. ITU-R BT.709-6 (06/2015) table item 1 footnote (1), pdftotext -layout lines 163-170; Rec. ITU-R BT.1886-0 (03/2011) Annex 1, pdftotext -layout lines 134-155; [producer working copy; not public] sha256 c63016c5859b7c7f (equal to producer pin S7); Table for TransferCharacteristics, pdftotext -layout line 1013; title line 8; curator grep across the three pdftotext extracts"
    },
    {
      "url": "https://www.itu.int/dms_pubrec/itu-r/rec/bt/R-REC-BT.1886-0-201103-I!!PDF-E.pdf",
      "note": "ARRI ALEXA Log C Curve in VFX (revision history to 09-Mar-17), pdftotext -layout lines 39-42, 94-99, 117, 124, 199-207; Rec. ITU-R BT.709-6 (06/2015) table item 1 footnote (1), pdftotext -layout lines 163-170; Rec. ITU-R BT.1886-0 (03/2011) Annex 1, pdftotext -layout lines 134-155; [producer working copy; not public] sha256 c63016c5859b7c7f (equal to producer pin S7); Table for TransferCharacteristics, pdftotext -layout line 1013; title line 8; curator grep across the three pdftotext extracts"
    },
    {
      "url": "https://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-H.273-202407-I!!PDF-E&type=items",
      "note": "ARRI ALEXA Log C Curve in VFX (revision history to 09-Mar-17), pdftotext -layout lines 39-42, 94-99, 117, 124, 199-207; Rec. ITU-R BT.709-6 (06/2015) table item 1 footnote (1), pdftotext -layout lines 163-170; Rec. ITU-R BT.1886-0 (03/2011) Annex 1, pdftotext -layout lines 134-155; [producer working copy; not public] sha256 c63016c5859b7c7f (equal to producer pin S7); Table for TransferCharacteristics, pdftotext -layout line 1013; title line 8; curator grep across the three pdftotext extracts"
    },
    {
      "url": "https://www.arri.com/resource/blob/31918/66f56e6abb6e5b6553929edf9203ed71/2017-03-alexa-logc-curve-in-vfx-data.pdf",
      "note": "ARRI ALEXA Log C Curve in VFX (revision history to 09-Mar-17), pdftotext -layout lines 39-42, 94-99, 117, 124, 199-207; Rec. ITU-R BT.709-6 (06/2015) table item 1 footnote (1), pdftotext -layout lines 163-170; Rec. ITU-R BT.1886-0 (03/2011) Annex 1, pdftotext -layout lines 134-155; [producer working copy; not public] sha256 c63016c5859b7c7f (equal to producer pin S7); Table for TransferCharacteristics, pdftotext -layout line 1013; title line 8; curator grep across the three pdftotext extracts"
    }
  ]
}
```

Evidence claims:
- [inference] ARRI Log C stores relative scene exposure, logarithmic in stops (about 78 10-bit code values per stop), and ARRI describes two ways to display it: the camera's tone-mapping or a linear conversion with display correction, where values above 1.0 may clip. Rec.709 video is adjusted so the picture looks right on a BT.1886 reference monitor (EOTF exponent 2.404) in a BT.2035 environment. Both can sit in the same pixel container, so treat a file as log or as display video according to its signal metadata or documentation, not by appearance. H.273 code 2 means the transfer characteristics are unspecified and left to the application. The words scene-referred and display-referred are not used in these texts; they are convenient shorthand for ARRI's scene exposure versus BT.709's viewed picture (F1, confirmed by curator search). · locator: ARRI ALEXA Log C Curve in VFX (revision history to 09-Mar-17), pdftotext -layout lines 39-42, 94-99, 117, 124, 199-207; Rec. ITU-R BT.709-6 (06/2015) table item 1 footnote (1), pdftotext -layout lines 163-170; Rec. ITU-R BT.1886-0 (03/2011) Annex 1, pdftotext -layout lines 134-155; [producer working copy; not public] sha256 c63016c5859b7c7f (equal to producer pin S7); Table for TransferCharacteristics, pdftotext -layout line 1013; title line 8; curator grep across the three pdftotext extracts · source: https://www.itu.int/dms_pubrec/itu-r/rec/bt/R-REC-BT.709-6-201506-I!!PDF-E.pdf

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

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