# How does ARRI embed camera and lens metadata in SDI (KLV in ANC packets), and what do the lens fields, including the newly documented effective focal length and entrance pupil, say?

- id: art_01M5MRVAZ3JZC4SGHRYGQHYKVQ
- 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, T19 · tags: none
- updated: 2026-10-23T16:17:34.683Z
- url: https://veyrul.com/articles/art_01M5MRVAZ3JZC4SGHRYGQHYKVQ

ARRI sends extended camera metadata over SDI as the 4096-byte ArriFileV3 header wrapped in SMPTE 336M-2007 KLV (BER length 83 00 10 00) and a separate 12-bit LUT KLV of 6144 bytes (83 00 18 00), segmented into SMPTE 291M ANC packets. ALEXA 35 SUP 1.2 adds lens fields LDI26 and LDI27 in micrometres; LDI26 is named 'Lens Effective Focal Length' (back nodal point to back focus point) in the change notes but 'Axial Effective Focal Length' in the field table, and LDI27 is the entrance pupil position.

ARRI sends extended camera metadata over SDI as the 4096-byte ArriFileV3 header wrapped in SMPTE 336M-2007 KLV (BER length 83 00 10 00) and a separate 12-bit LUT KLV of 6144 bytes (83 00 18 00), segmented into SMPTE 291M ANC packets. ALEXA 35 SUP 1.2 adds lens fields LDI26 and LDI27 in micrometres; LDI26 is named 'Lens Effective Focal Length' (back nodal point to back focus point) in the change notes but 'Axial Effective Focal Length' in the field table, and LDI27 is the entrance pupil position.

Curator qualifications: Document read 2026-10-22; no SDI stream decoded. Older ARRI metadata white paper (LDI04 in 1/1000 mm, carrier mapping) not re-read (producer). VANC line numbers not re-checked.

Limitations: Document read 2026-10-22; no SDI stream decoded.

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

```json
{
  "citations": [
    {
      "url": "https://www.arri.com/resource/blob/327826/a17ae3b8bf7e8d487d6d01648bdf432e/arri-cameras-sdi-metadata-white-paper-data.pdf",
      "note": "ARRI cameras SDI metadata white paper, sections 4 (change notes), field table, 6.1-6.2.3"
    },
    {
      "url": "https://www.arri.com/resource/blob/31912/e9674189f2ed77d45912681b9e0a168f/2018-10-17-arri-metadata-white-paper-alexa-lf-data.pdf",
      "note": "ARRI cameras SDI metadata white paper, sections 4 (change notes), field table, 6.1-6.2.3"
    }
  ]
}
```

Evidence claims:
- [sourced_fact] ARRI sends extended camera metadata over SDI as the 4096-byte ArriFileV3 header wrapped in SMPTE 336M-2007 KLV (BER length 83 00 10 00) and a separate 12-bit LUT KLV of 6144 bytes (83 00 18 00), segmented into SMPTE 291M ANC packets. ALEXA 35 SUP 1.2 adds lens fields LDI26 and LDI27 in micrometres; LDI26 is named 'Lens Effective Focal Length' (back nodal point to back focus point) in the change notes but 'Axial Effective Focal Length' in the field table, and LDI27 is the entrance pupil position. · locator: ARRI cameras SDI metadata white paper, sections 4 (change notes), field table, 6.1-6.2.3 · source: https://www.arri.com/resource/blob/327826/a17ae3b8bf7e8d487d6d01648bdf432e/arri-cameras-sdi-metadata-white-paper-data.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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