The develop preferred cam_xyz, whose rows are the XYZ of each camera channel and
which nothing normalised: on the ORF this was reported on it left the frame
green and blue (R/G 0.921, B/G 0.886) where the file's own preview sits at
1.013 / 0.841, and saturated reds came back as the dark purple the frame was
reported for — a red pixel's green ran negative through a row that carries
-2.64, so it clipped to 0 while the knee pulled red down with it.
LibRaw hands back dcraw's own rgb_cam, already the camera -> sRGB transform with
rows summing to one, and it is now applied as handed back: R/G 1.020 B/G 0.920,
and the fit against the embedded preview follows to mean 167.5,164.8,138.5
against the preview's 167.0,164.8,138.6 and the camera's own JPEG's 165,162,133.
Dividing rgb_cam by pre_mul — which carries that row normalisation — is what the
frame before this one did instead, and it undoes it.
The cam_xyz chain stays as the fallback for a file with no rgb_cam, with its
rows normalised so a neutral frame opens neutral. invert3x3, unused since the
frame stopped going through the chain, is dropped.
3dtours
2e36acd18b