Colour Measurement

How colour is measured with instruments rather than eyes: colorimeters, spectrophotometers, measurement geometry, standard observers and illuminants, and what a ΔE number does and does not tell you.

Describes measurement principles and published standards in summary. Instrument brand recommendations are out of scope.

11 topics · 46 evidence-labelled claims · 24 sources

Tools

ΔE colour difference calculator

Instruments

What each kind of instrument measures.

What is the difference between a colorimeter and a spectrophotometer?A colorimeter measures colour through three filters shaped like the eye's colour-matching functions and reports tristimulus value…What does a spectroradiometer measure that a spectrophotometer does not?A spectroradiometer measures light itself — the spectral power emitted by a lamp, a display or the sky, in absolute radiometric u…How is colour measured for opaque, translucent and transparent materials?Opaque materials are measured in reflectance: the instrument lights the surface and reports the fraction reflected at each wavele…

Conditions

Geometry, observers, illuminants and calibration.

What do 45°/0° and d/8° mean, and why do they give different readings?Measurement geometry is the angle at which an instrument lights the sample and the angle at which it collects the reflected light.What is the difference between SCI and SCE measurement?SCI (specular component included) measures all the light a sample reflects, including the mirror-like gloss reflection; SCE (spec…What are the 2° and 10° standard observers, and which should I use?A standard observer is a set of three colour-matching functions describing an average person's colour vision, from which XYZ and…What are CIE standard illuminants, and why do D50 and D65 both exist?A CIE illuminant is a table of relative spectral power — a defined 'light' for calculating colour — not a physical lamp.How accurate is a colour measurement, and how do I know?Three different numbers describe it.

Colour difference

ΔE formulas, tolerances and their limits.

What is ΔE, and why do ΔE76, ΔE94 and CIEDE2000 give different numbers?ΔE is a single number for the difference between two colours, calculated from their CIELAB values.What ΔE tolerance is acceptable, and how do industries set one?There is no universal acceptable ΔE.Why does the 'nearest' colour by ΔE sometimes look like the wrong match?Because ΔE formulas model average judgements of two large, flat, adjacent samples on a neutral background under standard light.