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Issue #150: Raw: NEF colour from the camera JPEG; 12-bit NEF black level

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LightCraft has no colour matrix for Nikon cameras. Because of this, NEF
files showed colours that were too gray and too green.

- Colour: LightCraft now calculates a colour matrix and a tone curve from
  the JPEG preview in each NEF file. Sony ARW files use the same
  procedure and the same quality checks. White balance is relative to
  the as-shot look, as for ARW files.
- One function, camera_preview::file_local_look, selects the formats for
  the fit and for the relative white balance. Photo::relative_wb in the
  catalog uses the same formats.
- Black level: Nikon stores the black level (maker note 0x003d) in
  14-bit units, also in 12-bit files. The decoder read it as a 12-bit
  value. Because of this, 12-bit files from the D750, D780, D850, D7500
  and Z 50 were too dark. Now the decoder divides the value by 4 for
  12-bit files.
- The corpus gets the D7500 12-bit and 14-bit lossless samples. A test
  compares their levels. The render cache version increases to 9.

Results on 13 NEF files that LightCraft can decode: LightCraft accepted
the fit for all 13 files. The mean colour difference from the camera
JPEG (CIE76 dE) decreased from 13-46 to 2.9-7.8. One file with mixed
light improved by a small quantity only (12.7 to 12.0).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
This commit is contained in:
Trey Reynolds
2026-10-06 19:26:45 -05:00
co-authored by Claude Opus 5.5
parent 5cee0c08d0
commit 22c6aa6918
11 changed files with 159 additions and 27 deletions
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xtask/src/main.rs
+8
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@@ -281,6 +281,14 @@ const RAW_SAMPLES: &[(&str, &str)] = &[
"nef-nikon-d7000-lossy12.nef",
"https://raw.pixls.us/getfile.php/961/nice/Nikon%20-%20D7000%20-%2012bit%2012bit%20compressed%20%28Lossy%20%28type%202%29%29%20%283:2%29.NEF",
),
(
"nef-nikon-d7500-lossless12.nef",
"https://raw.pixls.us/getfile.php/1532/nice/Nikon%20-%20D7500%20-%2012bit%2012bit%20compressed%20%28Lossless%29%20%283:2%29.NEF",
),
(
"nef-nikon-d7500-lossless14.nef",
"https://raw.pixls.us/getfile.php/1534/nice/Nikon%20-%20D7500%20-%2014bit%2014bit%20compressed%20%28Lossless%29%20%283:2%29.NEF",
),
(
"nrw-nikon-b700-uncompressed.nrw",
"https://raw.pixls.us/getfile.php/1621/nice/Nikon%20-%20COOLPIX%20B700%20-%2012bit%2012bit%20uncompressed%20%284:3%29.NRW",