Where does chromatic collide?

In colour science, chromatic adaptation is the visual system's adjustment to the colour of the prevailing illumination, so that familiar object colours look roughly the same as the light shifts (say from daylight to tungsten), which is the basis of colour constancy and of the white-balance correction cameras apply. Wyszecki and Stiles's Color science sets out the quantitative transforms. The referent is a shift in the colour balance of perception or of a captured image under a change of light source, modelled rather than cured.[1]

Unit

The shift in colour balance induced by a change of illuminant

Recovery means

Not applicable

Measured by

Modelled by chromatic-adaptation transforms mapping tristimulus values between illuminants

In music theory, “chromatic” refers to pitches drawn from the full twelve-semitone collection rather than the seven notes of the prevailing key: the chromatic scale ascends by semitones, and chromaticism is the expressive use of non-diatonic tones and the harmonies built from them. Piston's Harmony treats its use and voice-leading. The referent is tonal material lying outside the diatonic set of the key, and the word's colour meaning is purely metaphorical, unrelated to light sources or graph colouring.[2]

Unit

The degree of departure from the diatonic (key) collection

Recovery means

Not applicable

Measured by

Analysed by identifying non-diatonic pitches and chords relative to the prevailing key

In graph theory, the chromatic number of a graph is the minimum number of colours needed to assign one colour to each vertex so that no two adjacent vertices share a colour. West's Introduction to graph theory develops the idea; it measures a graph's colouring complexity and underlies scheduling, register allocation, and frequency-assignment problems. The referent is an integer invariant of the graph's structure, and “colour” here is a formal label with no relation to light or to musical pitch.[3]

Unit

The minimum number of colours (an integer)

Recovery means

Not applicable

Measured by

Determined by proper-colouring algorithms and bounds such as the clique number and maximum degree