The same green spot color, measured against the same target: one report says ΔE 3.2, another says ΔE 1.3. Neither instrument is broken. They are using different formulas — and on press, a tolerance of "ΔE 2" means something very different depending on which one it is written in.
If you need a refresher on what ΔE is and why it matters, start with our ΔE primer. This article is about the part that trips up operators and buyers alike: ΔE is not one number, but a family.
ΔE76: a straight line
The original formula, CIE 1976, is the simplest one imaginable. Each color is a point in L*a*b* space — lightness, red–green, yellow–blue — and ΔE76 is the straight-line distance between the two points.
Simple, and wrong in a predictable way. L*a*b* was designed to be perceptually uniform, and it is not quite. The same distance looks larger in some regions of color space than in others. In saturated colors, ΔE76 exaggerates differences the eye barely registers. Near the neutral axis — greys, pastels, near-whites — it can understate differences the eye catches immediately.
ΔE00: a line that bends
CIEDE2000, usually written ΔE00, was built to correct exactly that. It keeps the L*a*b* coordinates but weights the lightness, chroma and hue differences separately, adds a correction for the blue region where hue perception behaves differently, and adjusts near-neutral colors. It is standardized as ISO/CIE 11664-6.
In between sits ΔE94, an intermediate step you will still meet in older specifications, and CMC, common in textiles. In printing and packaging, ΔE00 is increasingly the default in new specifications.
The same pairs, two formulas
The numbers below are not invented. They come from the reference test data published with the CIEDE2000 formula (Sharma, Wu and Dalal, 2005), which every implementation is checked against — including the one we used to compute the ΔE76 column.
A saturated green, drifting in yellow–blue: ΔE76 = 3.18, ΔE00 = 1.26.
A deep, saturated blue, drifting in hue: ΔE76 = 4.00, ΔE00 = 2.04.
A near-neutral grey, picking up a slight cast: ΔE76 = 2.24, ΔE00 = 2.37.
A near-neutral crossing from a reddish to a greenish cast: ΔE76 = 4.98, ΔE00 = 7.18.
Read them as an operator would. Against a ΔE 2 tolerance, the green fails in ΔE76 and passes comfortably in ΔE00. The grey fails in both. And the last pair — a neutral flipping from a reddish cast to a greenish one — is the kind of shift a customer spots at once on a light label; ΔE00 scores it as larger than ΔE76 does.
There is no fixed conversion factor between the two. The ratio depends on where the color sits, which is precisely the point of ΔE00.
Test your own eye
The pairs above are what the formulas say. To see what your own eye says, try these two games from ColorLoop, developed by VEORIA. Both put you in front of nearly identical brand colors — and Brand match tells you how far off you were, in ΔE00.
AWhat it means on press
Read the specification for the formula, not just the number. "ΔE ≤ 2" is not a tolerance until it says which ΔE. A brand owner specification should state the formula, and the illuminant and observer (typically D50, 2°).
Make every instrument report in the same formula. If the inline system on press reports ΔE76 and the handheld at the quality desk reports ΔE00, operators will see two numbers for one color and stop trusting both. The same goes for the color software that stores the job record.
Never compare readings across formulas. A trend that switches formula halfway through a job is not a trend. Neither is a supplier comparison where one plant reports ΔE76 and the other ΔE00.
Re-set tolerances when the formula changes. Because ΔE00 compresses differences in saturated colors, a ΔE76 tolerance of 2.0 copied over as ΔE00 2.0 effectively loosens it on bright spot colors — and can tighten it near neutrals. When a specification changes formula, the tolerance values have to be set again, not copied.
Where DeltaOne fits
The DeltaOne operator screen shows every ink against its target in a ΔE2000 table, alongside solid density and dot gain, refreshed on every revolution. When a color moves, the operator sees it in the same formula the specification uses — not in a number that has to be translated first. For the questions to ask any color system about formulas and illuminants, see our ten questions for color and inspection vendors, or see DeltaOne on a running press.
