Delta E, color difference/deviation

Delta E, color difference/deviation (In French différence entre deux couleurs) delta E, dE, ΔE difference between two chromaticity coordinates in a perceptually equidistant color space. It is calculated with the so-called Euclidean difference formulae, the root of the sum of the color coordinate squares – see back inside cover pages: CIELAB. To prevent confusion with color differences that were calculated using a color difference formula from a different color system, a complete Delta E specification contains as an index the reference to the color system in question, e.g. ΔE*ab for CIELAB (1976), also supplemented by the observation conditions, e.g. 2°/D50 for 2° standard observer field of view with 5000 Kelvin as illuminant. In the printing industry, the Delta E value is particularly suitable for agreeing on tolerances in standards as well as between customers and print providers with respect to the criteria for the accuracy of color reproduction in accordance with ISO 12647 or PSO or even closer tolerances in individual cases. Practical statement of the Delta E value: 0.0 to 0.2 “unnoticeable” (non perceptible), up to 0.5 “very small” (très faible), up to 1.0 “noticeable” (perceptible), up to 1.5 “small” (faible), up to 2.0 “just right noticeable” (tout juste nettement discernable), up to 3.0 “distinctive” (nette), up to 4.0 “marginally disturbing” (peu gênante), up to 6.0 “medium, very distinctive” (moyenne, très nette), over 6.0 “large, disturbing” (importante, forte, gênante).