Colour Difference Formulae Questions and Answers

Answer: A

The signs indicate the direction of correction required in the recipe. Consistency in the subtraction convention is essential to avoid reversing them. Signs indicate the direction of correction. Consistency avoids reversing the correction.

Answer: B

Both are true and the reason gives the risk, and batch minus standard is the usual convention. A reversed sign sends the correction in the wrong direction. The convention must be stated explicitly. A sign error sends production the wrong way.

Answer: C

Texture affects both the instrumental reading and the visual impression. Parametric factors and careful sample presentation both address it. Texture affects instrument and eye alike. Presentation is standardised for that reason.

Answer: D

Correct answer: 1 and 2 only

Statements 1 and 2 are correct: a textured surface scatters differently depending on how it is presented, which alters both the reading and the appearance. Statement 3 is the opposite of the truth - texture is precisely why sample presentation must be standardised, with the number of layers, the orientation and the aperture all specified.

Answer: A

A translucent single layer would let the backing influence the reading. Standard practice specifies the number of layers for each fabric type. A translucent sample lets the backing show through. Layer count is specified by fabric type.

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. Light passes through a single layer of most fabrics, so some of what the instrument reads is the backing rather than the sample. Folding to a stated number of layers - usually until adding another changes nothing - makes the reading independent of what lies behind.

Answer: C

Reproducibility by contrast concerns agreement across instruments or laboratories. Both are quoted in the specification of a measuring instrument. Each answers a different reliability question. All are quoted in an instrument specification.

Answer: D

Each answers a different question about the reliability of a number. An instrument may be repeatable without being accurate at all. Consistency and correctness are separate matters. A systematic offset leaves repeatability untouched.

Answer: A

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. Repeatability measures the spread of successive readings of the same sample; accuracy measures agreement with the true value. An instrument with a systematic offset reproduces that offset faithfully every time, so it is precise and wrong - which is why calibration against a standard is a separate exercise from checking repeatability.

Answer: B

Correct answer: small absolute measurement errors produce large lightness differences

\( L^* \) is a cube root function of the luminance factor, so its slope is steepest near black. A small absolute error in reflectance at the dark end therefore produces a disproportionate change in lightness, and dark shades are correspondingly harder to control - a fact reflected in the wider tolerances usually agreed for them.