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* raw: fit non-DNG colour to the camera's embedded JPEG * raw: preserve fitted Camera Raw look and crop D5100 borders --------- Co-authored-by: Gert Pellin <gert@pellin.be> Co-authored-by: optimalbytee <optimalbytee@users.noreply.github.com> Co-authored-by: Brandon Thomas <echelon@gmail.com> Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
61 lines
3.4 KiB
Markdown
61 lines
3.4 KiB
Markdown
# Nikon D5100 NEF development
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Validated 2026-10-11 with three locally supplied NEFs: DSC_0453 (portrait),
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DSC_0469 and DSC_0477. Photos, extracted previews and metadata dumps stay local;
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regression fixtures are synthetic.
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## Findings and change
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All three files contain 4992 × 3280, 14-bit Nikon lossy type-2 sensor data
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with a normal `44 20` linearization table. Their as-shot white balances are
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already decoded correctly. They have no colour calibration, so the neutral
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fallback treats white-balanced camera channels as linear sRGB and looks flat.
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The Nikon `44 40` quarter-span decoder issue addressed elsewhere does not apply.
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This branch uses the existing embedded-JPEG rendering work in
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[PhotoCraft #2135](https://github.com/storytold/photocraft/pull/2135), head
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`d1a91d1f0dff1ed7ac74767b602051e88198b2e5`. That work fits a matrix and monotone
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tone curve with held-out acceptance checks. It supplies the appearance fix;
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this follow-up preserves that rendering in `import_raw_tuned`. Fitting happens
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at default exposure and camera WB before applying user controls, so changing
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Exposure, Temperature or Tint cannot be absorbed by a new fit. Unusable previews
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still use the documented neutral fallback, and calibrated sensors skip fitting.
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Aligning green-channel gradients of the developed sensor plane against each
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camera's full 4928 × 3264 JPEG identifies the same (8, 8) crop origin. Searching
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even offsets x=0…56, y=0…16 gives best normalized correlations of 0.944, 0.698
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and 0.684 for the three files respectively. A model- and sensor-size-matched
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D5100 image-area entry removes the magenta edge and applies before orientation;
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portrait output is 3264 × 4928. It preserves an explicit file crop and leaves
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black, white, WB and colour calibration unchanged.
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The camera JPEG is a rendering reference, not a calibration chart. Its picture
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style, local tone mapping and clipping cannot all be reproduced by one matrix
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and curve. No D5100 colour matrix or unrelated camera profile was added.
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After applying the measured crop, all three fits pass their held-out acceptance
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checks. Mean CIE76 ΔE on the held-out grid against each camera JPEG is:
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| File | Neutral fallback | Fitted rendering | Final upright size |
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|---|---:|---:|---|
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| DSC_0453 | 13.68 | 2.07 | 3264 × 4928 |
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| DSC_0469 | 13.90 | 2.45 | 4928 × 3264 |
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| DSC_0477 | 7.62 | 1.62 | 4928 × 3264 |
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These values measure appearance against the file's JPEG, not calibration accuracy.
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Full-resolution default, +0.5 EV and Temperature +20/Tint −15 imports were exported
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for each file and independently verified as RGB16 TIFFs with the ProPhoto-compatible
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ICC profile. Default tuned pixels and ICC bytes equal normal import exactly. Local
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whole-frame and 100% edge comparisons were inspected against the camera JPEG and
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installed LightCraft 0.6.0: the border is gone and colour/contrast improve, with
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remaining differences in sunset highlight saturation and noise/detail rendering.
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## Regression coverage
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Synthetic tests verify identical normal/default-tuned pixels, preserved fitted
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appearance with positive/negative exposure and WB edits, exact application of
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user gains after fitting, neutral fallback for missing or unsuitable previews,
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and graceful truncated-input handling. Image-area tests verify the D5100 crop,
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unchanged sensor metadata, explicit-crop precedence and exact model/size guards.
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All final imports retain 16-bit RGB in the ProPhoto-compatible working profile.
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