Colour Vision and Observer Questions and Answers

Answer: C

Correct answer: the amount of each primary needed to match each wavelength

The matching functions are the experimental results themselves: for each monochromatic wavelength, how much of each of the three primaries was needed to match it. They depend on the primaries chosen, which is why the RGB and XYZ functions look quite different while describing the same visual system.

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. Any set of matching functions is some fixed linear combination of the three cone sensitivities, with the coefficients set by the primaries used. This is why different primary sets give different-looking functions describing identical vision, and why the cone fundamentals can be recovered from the matching data by a transformation.

Answer: A

They are the physiologically meaningful quantities underlying the matching functions. The CIE 2006 system is built on them rather than on the older empirical functions. Fundamentals are the physiologically meaningful quantities.

Answer: B

Correct answer: 1 and 2 only

Statements 1 and 2 are correct: the cone fundamentals are the spectral sensitivities of the three cone types, and they are a linear transformation away from any set of colour matching functions. Statement 3 describes a different kind of experiment entirely - hue naming is a judgement of appearance, not a match, and cannot yield receptor sensitivities.

Answer: C

It allows the observer to be specified by age and field size rather than fixed. Adoption in industry has been slow because of the weight of existing data on the older system. Age and field size become explicit parameters.

Answer: D

Both are true and the reason gives the inertia, and changing observer would invalidate stored tolerances. Continuity often outweighs technical improvement in an established industry. Stored tolerances rest on the older observer.

Answer: A

Correct answer: the luminance level falls low enough for rods to contribute

At mesopic levels the rods are still responding, and since they have a spectral sensitivity of their own their signal disturbs the cone-based match. A match set at a low light level can therefore fail at a higher one. Assessment is carried out at a specified and adequate illuminance to keep the rods out of it.

Answer: B

Rod intrusion at low levels invalidates the standard observer functions. Minimum illuminance levels are specified to keep assessment in the photopic range. Cone vision alone is assumed throughout. Minimum illuminance levels are specified accordingly.

Answer: C

Cones are directionally sensitive and respond less to obliquely incident light. It reduces the effect of optical aberrations at large pupil diameters. Cones respond less to obliquely incident light. Aberration at wide pupils is reduced by it.

Answer: D

Sample reflectance is a property of the object rather than of the observer. The other three are all individual characteristics of the eye itself. Reflectance belongs to the sample instead. Only the first three describe the observer.