Colour Difference Formulae Questions and Answers

Answer: C

Both are true and the reason gives the reason, and the lightness function amplifies it further. Black trap measurements are used to characterise stray light. Dark samples are the most demanding case. Stray light and lightness slope compound there.

Answer: D

The first two are correct and compound one another. The third is the opposite of the truth, since dark samples are among the most demanding to measure well. Two effects compound one another there. Black trap measurements characterise the stray light.

Answer: A

They were fitted on small difference data and extrapolate poorly. A Delta E of thirty conveys little beyond the fact that the colours are different. The formulae were fitted on small differences. Extrapolation beyond that range is unsound.

Answer: B

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason gives the mechanism. The formulae were fitted to visual judgements of small differences, so their weighting functions are calibrated for that range. A value of 40 tells you the two colours are quite different, which was already obvious, and its precise size carries no reliable meaning.

Answer: C

Large differences fall well outside the range the formulae were fitted on. The other three all concern the small differences they were designed for. Large differences fall outside the fitted range. The number becomes a label rather than a measure.

Answer: D

It grounds the number in what the customer has actually accepted before. Purely theoretical tolerances frequently prove impractical in production. Historical acceptance grounds the number in reality. Theory alone frequently proves impractical.

Answer: A

The first two are correct and reflect sound practice. The third would reject the great majority of commercially satisfactory production. Threshold is far tighter than commercial tolerance. Most acceptable production would be rejected.

Answer: B

Every stored tolerance would need re-establishing against visual judgements. The cost of that exercise outweighs the modest gain in accuracy. Every stored tolerance would need re-establishing. The cost outweighs the modest gain.

Answer: C

Correct answer: the CIE colour rendering index

The rendering index measures how faithfully a light source reveals colours compared with a reference illuminant - a property of the source, not a difference between two samples. CMC, CIEDE2000 and \( \Delta E^*_{ab} \) are all colour difference formulae, differing only in how they weight the components.

Answer: D

Without agreement the two parties compute different numbers from the same material. Disputes then become impossible to settle on the evidence. Both parties must compute the same number. Disputes are otherwise unresolvable on evidence.