Colour Difference Formulae Questions and Answers

Answer: A

Departures from these conditions are handled by the parametric factors. Quoting a value without noting the conditions omits part of the specification. Conditions belong with the number reported. Reference conditions were assumed in the fitting.

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 same measured pair can give 1.8 by \( \Delta E^*_{ab} \), 1.1 by CMC and 0.9 by CIEDE2000, because each weights the components differently. A figure quoted without its formula cannot be compared with any other, and a tolerance quoted without one cannot be applied.

Answer: C

The shape of that region depends on the formula chosen. Delta E ab gives a sphere while the weighted formulae give an ellipsoid oriented to the space. Shape follows directly from the weighting used. Equal weights give a sphere in the space.

Answer: D

Both are true and the reason gives the geometry, and weighted formulae give ellipsoids instead. The ellipsoid shape matches visual tolerance far better. Equal weighting produces a sphere instead. Visual tolerance is ellipsoidal rather than spherical.

Answer: A

The first two are correct and follow from the formulae. The third is not so, and batches accepted by one may be rejected by the other. Shape as well as size differs between them. Acceptance sets therefore differ in membership.

Answer: B

Chroma differences are tolerated more readily than hue differences at high chroma. Hue is the most critical direction in most commercial assessments. Chroma is tolerated more readily than hue. Ellipsoids stretch along the chroma direction.

Answer: C

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 eye is more sensitive to a shift in hue than to an equivalent shift in lightness or chroma, so a hue error is noticed first and objected to hardest. This is why tolerance ellipsoids are shortest in the hue direction and why CMC and CIEDE2000 weight that component most tightly.

Answer: D

Correct answer: about 1

A \( \Delta E^*_{ab} \) of about one is the conventional rule of thumb for a just noticeable difference, and it is useful as an order of magnitude. It should not be taken as a threshold: the true value ranges from well under one near the neutral axis to several units at high chroma, which is the whole reason the weighted formulae were developed.

Answer: A

Correct answer: 1 and 2 only

Statements 1 and 2 are correct: unity is a serviceable rule of thumb, and the actual threshold varies greatly across the space. Statement 3 turns a rough guide into a precise claim, and it is false in both directions - a difference of one is clearly visible in some regions and quite invisible in others.

Answer: B

The appropriate value depends on the product, the price and the market. Fixing it at threshold would reject most commercially acceptable production. Market and product both bear on the choice. Threshold alone would be impractically tight.