Colour Science & Perception
what the eye settles, and what it cannot
Generator

A box tolerance and a ΔE tolerance around the same colour

A slice through CIELAB at L* 50, with the ΔE2000 = 1 contour traced point by point and a ±1 component box drawn over it. The contour is 2.1 times longer in one direction than the other, and the box is square. Of every sample either rule accepts, the two disagree about 74% — accepted by one specification and rejected by the other, on the same measurement.
A box tolerance and a ΔE tolerance around the same colourA slice through CIELAB at L* 50, with the ΔE2000 = 1 contour traced point by point and a ±1 component box drawn over it. The contour is 2.1 times longer in one direction than the other, and the box is square. Of every sample either rule accepts, the two disagree about 74% — accepted by one specification and rejected by the other, on the same measurement.gold outline: ΔE2000 = 1blue box: ±1 in each componentelongation 2.13disagree on 79%of everything either acceptsΔa*at L* 50, a* 55, b* 25 — the shape changes elsewheresame measurement, two verdictsCIE 1931 2° observer

Drawn at its defaults, in colour in practice. It takes no options at all, so every essay calling it gets this exact drawing.

Called by 3 essays

the blast radius of changing it

Difference and uniformity

A tolerance is a shape

A total colour difference below one, or every component within one — the two sound like the same requirement stated twice. They are different shapes, they disagree about most of what either accepts, and which one a supplier is held to is worth money.

 Difference and uniformity

Where the formula is not smooth

A colour difference formula is a distance, and a distance ought to vary gently. CIEDE2000's does not everywhere — it carries a hue-rotation term with a hard edge in it, and the discontinuity sits where a great many industrial samples live.

 Difference and uniformity

A tolerance is a probability

A colorimeter reports one number and a specification compares it with another, and both are computed for an observer who does not exist. Handed to two hundred people, the same pair at ΔE00 1.0 is read from 0.8 to 3.7 — and which of those two ranges applies depends on something no specification records.

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