Colour & Colour Management — 18 Terms Defined

Camera Profile Colour & Colour Management A description of how a particular camera model renders colour, applied during raw conversion to translate sensor values into a colour space.

Chroma Colour & Colour Management C* (CIELAB) The colourfulness of an area judged relative to the brightness of a similarly lit white, a perceptually defined counterpart to saturation.

Chromatic Adaptation Colour & Colour Management The visual system's automatic adjustment to the colour of the prevailing light, which keeps familiar objects looking the same colour under different illuminants.

CIE Chromaticity Diagram Colour & Colour Management CIE xy The horseshoe-shaped plot of all colours visible to human vision, on which colour space gamuts are drawn as triangles.

CIELAB Colour & Colour Management L*a*b* A device-independent colour model with one lightness axis and two opponent colour axes, designed so equal numerical steps look equally different. ΔE = √(ΔL*² + Δa*² + Δb*²)

Colorimeter Colour & Colour Management An instrument that measures colour through three filters approximating human vision, used mainly for calibrating displays.

Colour Banding Colour & Colour Management bits Visible steps in what should be a smooth gradient, caused by too few tonal levels to render the transition continuously.

Colour Cast Colour & Colour Management An unwanted overall tint across an image, usually caused by the light source or by reflections from coloured surfaces.

Colour Checker Colour & Colour Management patches A card of printed patches with known colour values, photographed in a scene to allow accurate colour correction and profiling.

Colour Constancy Colour & Colour Management The perceptual effect by which an object keeps its apparent colour across widely different illuminants.

Colour Grading Colour & Colour Management The deliberate shaping of an image's colour for stylistic effect, as distinct from correcting it toward accuracy.

Colour Harmony Colour & Colour Management A relationship between the colours in an image that the viewer perceives as coherent rather than accidental.

Colour Management Colour & Colour Management The system of profiles and conversions that keeps colour consistent as an image moves between camera, screen, printer and web.

Colour Rendering Index Colour & Colour Management CRI (Ra) A score out of 100 describing how faithfully a light source reveals the colours of objects compared with a reference illuminant.

Colour Space Colour & Colour Management A defined set of colours, described by primaries, a white point and a transfer function, within which numerical colour values have a specific meaning.

Colour Temperature Colour & Colour Management K (kelvin) A measure of the colour of a light source, expressed as the temperature of a theoretical black body radiating the same hue.

Complementary Colours Colour & Colour Management Pairs of colours sitting opposite each other on the colour wheel, which produce maximum contrast when placed together.

Custom White Balance Colour & Colour Management K and tint Setting white balance by photographing a known neutral target under the actual light and telling the camera to treat it as neutral.