Generator
Correcting colour costs noise, and the two cannot both be least
Sweeping the colour matrix from its own diagonal — a white balance with no cross terms — to the full least-squares fit. Mean ΔE00 falls from 18.61 to 1.29; photon noise rises by a factor of 1.03. At 10000 photons per pixel.
Drawn at its defaults, in cameras, sensors and reproduction.
It reads 3 options and
no others: steps, photons, chroma.
Called by 2 essays
the blast radius of changing it
What a camera does
A camera profile is a fit
Since no matrix is exact, the one a manufacturer ships is a least-squares compromise over a set of surfaces somebody chose. Fitted on desaturated patches it is excellent on desaturated patches — and the sample set is a hidden argument to every camera profile in existence.
What a camera doesCorrecting colour costs noise
The matrix that turns a sensor's raw into XYZ has large off-diagonal terms of both signs, because that is what correcting a sensor which fails Luther's condition requires. Differences of large numbers are where noise grows, and the full correction amplifies photon noise by 1.66 times.