A raw shot in a monochrome picture style records full colour, but its
camera JPEG is grey: neither the full look nor the partial look has
colour to fit, so the photo started from the spectral matrices or the
neutral fallback with the default tone curve, about 1.3 EV darker than
the same body's colour-shot photos. The grey JPEG still shows the
camera's tone curve.
When no look was fitted and the JPEG is black and white (`monochrome`),
fit the quantile tone curve alone on top of the colour the photo gets
otherwise: the camera profile's (in `fit_preview`), else the spectral
matrices or the fallback (`monochrome_look`, after the spectral step).
The chroma curve stays neutral; the partial look's checks apply. A
tone-only look keeps the file's colour model for white balance.
LOOK_VERSION 2 -> 3, RENDER_CACHE_VERSION 42 -> 43.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
