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>
Sony bodies from before ~2017 (RX100–RX100M5, RX10, NEX, SLT, ILCE-6000,
A7/A7II/A7RII, ...) write no plain 0x7313/0x7310/0x74c7 tags in the raw IFD,
so the decoder used unit WB multipliers (strong green cast, e.g. the CC0
DSC-RX100M3 sample), black 512 (800 on 1-inch sensors), and kept padding
columns at the right edge.
- White balance: WB_RGBLevels from the maker note's enciphered Tag2010
block (layouts per ExifTool's Tag2010a..i tables; byte substitution
p^3 mod 249 checked black-box on 15 CC0 files: SonyISO matches Exif ISO,
ILCE-7M3 levels match its plain 0x7313).
- Black level: recovered from the encrypted SR2SubIFD by known-plaintext
analysis (constant key in every file; RX100M6/ILCE-7M3 plain 0x7310 as
plaintext; 8 keystream bytes at offset 2510, plausibility-checked).
- Crop: DNG DefaultCrop or the maker note's FullImageSize.
- "12-bit uncompressed" ARWs hold 14-bit-scale data: black/white follow it.
- Render cache version bumped; corpus manifest + corpus test, unit tests.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
The 0.055 cap rejected half of the public Sony samples tried (ILCE-6400,
ILCE-6700, ILCE-7M4) although their fits were 1.5-3x closer to the
camera JPEG than the fallback and visibly better (mean dE vs the embedded
preview 19-26 -> 5-10). Unrelated previews stay rejected (synthetic test
lands at 0.115).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
