Colour Science & Perception
what the eye settles, and what it cannot
Generator

One match, and what it says about the observer making it

The anomaloscope: a monochromatic 589 nm yellow set against a mixture of 545 and 670 nm. Only two cone classes respond at those wavelengths, so the match is two equations in two unknowns and has one solution for any observer whose two pigments differ. The bar is the fraction of the accepted band; the mark is the solution. A normal observer accepts 0.7 per cent of the scale; an observer whose two pigments are the same accepts all of it, because their two equations are one equation twice. Nothing here is fitted to clinical data: the pigments are the same template used for every observer here, at stated peaks, and the match is the solution of the linear system.
One match, and what it says about the observer making itThe anomaloscope: a monochromatic 589 nm yellow set against a mixture of 545 and 670 nm. Only two cone classes respond at those wavelengths, so the match is two equations in two unknowns and has one solution for any observer whose two pigments differ. The bar is the fraction of the accepted band; the mark is the solution. A normal observer accepts 0.7 per cent of the scale; an observer whose two pigments are the same accepts all of it, because their two equations are one equation twice. Nothing here is fitted to clinical data: the pigments are the same template used for every observer here, at stated peaks, and the match is the solution of the linear system.normal25 nm apart87.9% red · accepted band 0.7%protanomalous11 nm apart94.3% red · accepted band 1.0%deuteranomalous10 nm apart77.6% red · accepted band 5.2%protanopeone pigmentevery mixture matchesall 545 nmall 670 nmresidual ≤ 1% cone contrastpigments at 566 and 541 nm and closer

Drawn at its defaults, in matching, and the laws it rests on. It takes no options at all, so every essay calling it gets this exact drawing.

Called by 2 essays

the blast radius of changing it

Matching and measuring

The laws that make colour add up

Colorimetry is an integral, and an integral assumes matching is linear. Grassmann's four laws are exact for a linear observer, to floating point — and they fail at both ends of the light range, by two different mechanisms, leaving colorimetry an operating band of three and a bit decades that no standard states.

 Matching and measuring

One match names the observer

A yellow at 589 nanometres set against a mixture of 545 and 670 is two equations in two unknowns. It has one solution for a normal observer, a solution somewhere else for an anomalous one, and no unique solution at all for a dichromat — whose two equations are one equation twice.

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