Color Difference ΔE (Lab)
How far apart two colors are by their Lab values: ΔE76, ΔE94 and ΔE2000. Light D50, observer 2°, as in print.
Measuring conditions: light D50, observer 2°.
- swatches: reference on top, print below (screen colors are approximate)
- the a*b* plane: the arrow runs from the reference to the print, the circle is the tolerance
Outside the tolerance (by ΔE2000).
How it is calculated
ΔE76 is the distance between the points in Lab space: √(ΔL² + Δa² + Δb²). Simple, but it ignores that the eye sees differences differently in different colors.
ΔE94 (graphic arts) and ΔE2000 add corrections for lightness, chroma and hue (kL = kC = kH = 1). ΔE2000 follows the CIE standard formula. A guide: ΔE up to 1 is hardly seen, 2–3 is visible side by side.
ΔE76 = √(ΔL² + Δa² + Δb²) ΔE94, ΔE2000: corrections for lightness, chroma and hue
Worked example
Color 1: Lab (50; 2.6772; −79.7751). Color 2: Lab (50; 0; −82.7485).
ΔE76 = √(0² + 2.6772² + 2.9734²) = 4.00. ΔE2000 = 2.0425, the reference value from the Sharma test data.
An estimate: screen colors only approximate the Lab values (a screen is no substitute for a spectrophotometer reading).
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