Metamerism Questions and Answers

Answer: C

The first two are correct and are the practical diagnostic. The third reverses the meaning, since crossings are precisely what a spectral match does not have. Identical curves never cross at all. Crossings indicate metamerism rather than a match.

Answer: D

The correction removes any residual mismatch that would inflate the index. What remains under the test illuminant is the metamerism proper. Residual mismatch would otherwise inflate the figure. The correction isolates the illuminant effect.

Answer: A

Both are true and the reason gives the reason, and the two effects would be confounded. The correction isolates the illuminant dependence alone. Two effects would otherwise be confounded. Correction precedes the index calculation.

Answer: B

Correct answer: A-2, B-4, C-1, D-3

The correction methods differ in how they force the pair into agreement under the reference before the test illuminant is applied. A multiplicative correction scales the reflectance of one sample, an additive correction adds a constant to it, a parametric correction adjusts for the viewing conditions, and no correction simply reports the raw difference. Which was used must be stated, because the resulting index depends on it.

Answer: C

Correct answer: matches equally well under both the reference and the test

The index measures how much the match degrades between the two illuminants, so zero means it degrades not at all - not that the samples are identical, and not that the match is good. A poor match under the reference that is equally poor under the test has an index of zero, which is why the index is never reported alone.

Answer: D

Both are true and the reason gives the distinction, and the index tests only two illuminants. A third illuminant might still separate the pair. The index tests two illuminants and no more. A third could still separate the pair.

Answer: A

It shows only that the two chosen conditions give the same result. Identical curves are a far stronger condition than a low index. A third condition could still expose the pair. Identical curves are the stronger requirement.

Answer: B

Correct answer: a good match under the reference that will fail elsewhere

This combination is the classic metameric failure and the reason both figures are needed. Under the illuminant the recipe was formulated for, the batch looks right; move it to the customer’s shop lighting and the difference appears. The colour difference alone would have passed it.

Answer: C

The first two are correct and are the practical reason both are computed. The third does not follow, and the two are frequently reported together. Each answers a different practical question. Both are reported for that reason.

Answer: D

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 colour difference asks how well the pair matches under the reference; the index asks how much that match will deteriorate under another illuminant. A pair can score well on either alone, so a specification that names only one of them can be satisfied by a batch that fails in use.