Delta E (ΔE, dE2000) Delta E 2000 (CIEDE2000 Color Difference Formula)

What Delta E Measures

Delta E (ΔE) represents the distance between two colors in a defined color space, most commonly CIELAB (Lab*). It is used to quantify how different a displayed or printed color is from a reference target. For example, it measures how far a TV's rendering of a color patch deviates from the color that patch is supposed to be.

The original formula, CIE76, published by the CIE in 1976, is a straightforward Euclidean distance calculation in CIELAB space: ΔE = sqrt((L1-L2)² + (a1-a2)² + (b1-b2)²), where L*, a*, and b* represent lightness and the two color-opponent dimensions of the space.

Why CIEDE2000 Exists

CIE76's Euclidean math treats all regions of color space as uniform, but human vision does not perceive color differences uniformly across the spectrum. The same numerical distance in one hue region can look far more or less different to the eye than the same distance in another. An intermediate formula, CIE94, addressed part of this problem but not all of it. CIEDE2000, published in 2001, was developed by adding five corrections on top of that work. It introduces additional weighting parameters for lightness, chroma, and hue differences specifically to account for the non-uniform nature of human color vision.

Key Thresholds

Using the CIEDE2000 formula specifically, a value below 1 is generally considered an imperceptible difference between colors, while a value above 1 indicates a difference a human observer can perceive.

This is distinct from the just-noticeable-difference (JND) figure associated with the older CIE76 formula: under CIE76, a ΔE of approximately 2.3 (not 1.0) corresponds to a JND. All ΔE formula variants, including CIE76, were originally designed with the intent that a difference of 1.0 would represent a JND, but experimental evidence has since called that original design assumption into question, which is part of why later formulas like CIEDE2000 exist.

Beyond the strict JND threshold, industry sources describe a broader practical scale: a ΔE of roughly 1 to 2 is barely noticeable under close inspection, while a ΔE of 3 or greater is clearly visible and often considered unacceptable, depending on the industry and application.

CIEDE2000 vs. CIE76

Structurally, CIE76 is a simple geometric distance calculation with no perceptual weighting. CIEDE2000 is substantially more complex: it adds weighting factors to the lightness (ΔL*), chroma (ΔC*), and hue (ΔH*) components of the color difference so that the resulting number better matches how a human observer actually perceives the difference, rather than treating color space as geometrically uniform. Among the standardized Delta E formulas, CIEDE2000 is the most modern and most widely used for this reason.

In practice, Delta E is measured with a colorimeter, or in higher-end workflows a spectrophotometer, paired with calibration software. The instrument measures the color a display actually outputs, compares it against a reference standard, and reports Delta E values across a patch set covering many colors. This process typically yields both an average Delta E across all patches and a maximum (worst-case) Delta E for the set.

Common Confusions

A Delta E of 1 is not a universal, formula-independent JND. The value at which a difference becomes just noticeable depends on which formula is being used. CIE76 puts that threshold near 2.3, while CIEDE2000's own documentation cites 1 as the imperceptible/perceivable boundary. Citing a bare "Delta E of 1" without specifying the formula elides a real numerical difference between standards.

A low average Delta E across a measurement patch set does not guarantee the absence of visible outliers. Because average and maximum Delta E are reported separately, a display can post an excellent average score while still having one or more individual colors with a much higher, visibly perceptible error. The average alone does not characterize worst-case accuracy.