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Colour Science and Measurement [ Question No: 1 To 20 ] :
The chief practical advantage of an instrumental whiteness value over visual ranking is
Consider the following statements about the CIE whiteness formula.
1. It is defined only for illuminant D65.
2. It is valid only over a limited range of whiteness and tint.
3. It applies equally well to strongly coloured samples.
The value of colour matching software is greatest where
A spectral match option in matching software seeks a recipe whose
A metameric pair is defined as two samples that
Assertion (A): Regular transmission geometry is unsuitable for a scattering sample.
Reason (R): Light scattered out of the direct beam never reaches the detector at all.
Assertion (A): The sphere coating must be spectrally neutral as well as highly reflecting.
Reason (R): A coating with any spectral structure would colour every measurement made.
The gloss trap in an integrating sphere is used to
A spectrophotometer differs from a tristimulus colorimeter in that the spectrophotometer
Match each signed difference with its interpretation.
List I
A. Positive Delta L star
B. Negative Delta a star
C. Positive Delta b star
D. Negative Delta C star
List II
1. the batch is yellower than the standard
2. the batch is lighter than the standard
3. the batch is duller than the standard
4. the batch is greener than the standard
A colour difference formula fitted to visual data will perform best
A tolerance expressed as a Delta E value defines
CIELAB was introduced principally to provide
Assertion (A): Tristimulus values of an additive mixture are the sum of the components.
Reason (R): Grassmann's laws establish the linearity of additive mixing.
Adaptation state affects a colour judgement because
Consider the following statements about colour matching experiments.
1. The observer adjusts three primaries to match a test field.
2. The amounts required become the tristimulus values.
3. The observer is asked to name the colour being viewed.
Consider the following statements about maintaining a viewing cabinet.
1. Lamp hours are recorded and lamps replaced on schedule.
2. The interior surfaces must remain a specified neutral grey.
3. Lamps need replacing only when they fail to light at all.
Which of these correlated colour temperatures would be described as the warmest in appearance?
The colour temperature of a source is
Assertion (A): A white paper still appears white in dim light.
Reason (R): Lightness is judged relative to the surround rather than in absolute terms.
Total number of questions : 20
Number of answered questions : 0
Number of unanswered questions : 20
Colour Science and Measurement [ Question No: 1 To 20 ] :
The chief practical advantage of an instrumental whiteness value over visual ranking is
Your Answer : (Not Answered)
Correct Answer : A
Correct answer: a repeatable number that can be specified and audited between parties
The value of an instrumental measure is that it can be written into a contract. A number with stated conditions can be produced by the supplier, checked by the customer, and disputed on evidence, which visual ranking cannot support. It does not remove the need to view the sample, it does not extend to coloured samples, and it certainly does not remove the need to calibrate.
Consider the following statements about the CIE whiteness formula.
1. It is defined only for illuminant D65.
2. It is valid only over a limited range of whiteness and tint.
3. It applies equally well to strongly coloured samples.
Your Answer : (Not Answered)
Correct Answer : A
Correct answer: 1 and 2 only
Statements 1 and 2 are correct: the equation is defined for D65 only, and it is valid only over a bounded range of whiteness and tint, typically about 40 to 5Y minus 280 with a tint between plus and minus 3. Statement 3 is the opposite of the truth - the formula was fitted to near-white samples, and applied to a strongly coloured one it returns a number that means nothing.
The value of colour matching software is greatest where
Your Answer : (Not Answered)
Correct Answer : C
The investment is repaid across many matches rather than by any single one. A single shade repeated endlessly needs no prediction at all. The investment repays across many matches. A single repeated shade needs no prediction.
A spectral match option in matching software seeks a recipe whose
Your Answer : (Not Answered)
Correct Answer : A
It generally requires the same colourants as the standard used. The resulting recipe is more expensive but far more robust to a change of conditions. The same colourants are usually needed. Robustness is bought at some cost.
A metameric pair is defined as two samples that
Your Answer : (Not Answered)
Correct Answer : A
The tristimulus values coincide although the underlying spectra do not. Any change of illuminant or observer can therefore break the match. The tristimulus values coincide but the spectra do not. That coincidence is what makes the match fragile.
Assertion (A): Regular transmission geometry is unsuitable for a scattering sample.
Reason (R): Light scattered out of the direct beam never reaches the detector at all.
Your Answer : (Not Answered)
Correct Answer : B
Both are true and the reason gives the loss, and the sample appears darker than it is. Diffuse transmission collects the scattered light as well. Regular geometry would report the sample too dark. Scattered light must be collected too.
Assertion (A): The sphere coating must be spectrally neutral as well as highly reflecting.
Reason (R): A coating with any spectral structure would colour every measurement made.
Your Answer : (Not Answered)
Correct 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. Light bounces many times inside the sphere before reaching the detector, so any wavelength dependence of the coating is applied repeatedly and amplified. A coating that reflected slightly less in the blue would make every sample read slightly yellow, and no calibration on a white tile would fully remove it.
The gloss trap in an integrating sphere is used to
Your Answer : (Not Answered)
Correct Answer : C
Correct answer: remove the specular component from the measurement
The gloss trap is an opening in the sphere wall placed where the specular reflection from the sample falls, backed by a light-absorbing cavity. With it open the specular light is absorbed and the measurement is specular excluded; with it closed and made part of the sphere wall, the light is retained and the measurement is specular included.
A spectrophotometer differs from a tristimulus colorimeter in that the spectrophotometer
Your Answer : (Not Answered)
Correct Answer : A
Spectral data allows values to be recomputed for any illuminant and observer. A colorimeter commits to one condition at the moment of measurement. Spectral data can be reprocessed at any time. Nothing need be decided at the moment of reading.
Match each signed difference with its interpretation.
List I
A. Positive Delta L star
B. Negative Delta a star
C. Positive Delta b star
D. Negative Delta C star
List II
1. the batch is yellower than the standard
2. the batch is lighter than the standard
3. the batch is duller than the standard
4. the batch is greener than the standard
Your Answer : (Not Answered)
Correct 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.
A colour difference formula fitted to visual data will perform best
Your Answer : (Not Answered)
Correct Answer : A
CMC was fitted largely on textile data and performs well on textiles. Extrapolating a formula far beyond its fitting conditions is always a risk. CMC performs best on textile samples. Fitting conditions bound the reliable range.
A tolerance expressed as a Delta E value defines
Your Answer : (Not Answered)
Correct 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.
CIELAB was introduced principally to provide
Your Answer : (Not Answered)
Correct Answer : A
It includes lightness as well as chromaticity, which the two dimensional diagrams omit. Colour differences can be computed as distances within it. Lightness is included, unlike the flat diagrams. Differences become distances in three dimensions.
Assertion (A): Tristimulus values of an additive mixture are the sum of the components.
Reason (R): Grassmann's laws establish the linearity of additive mixing.
Your Answer : (Not Answered)
Correct Answer : C
Both are true and the reason gives the justification, and the arithmetic is straightforward. Subtractive mixing offers no comparable simplicity. Transmittances multiply rather than adding. Additive arithmetic does not carry over.
Adaptation state affects a colour judgement because
Your Answer : (Not Answered)
Correct Answer : A
Von Kries scaling models this as independent gain changes in the three channels. Standard practice allows a period of adaptation before any judgement is made. Von Kries scaling models the rescaling. Adaptation takes a minute or two to settle.
Consider the following statements about colour matching experiments.
1. The observer adjusts three primaries to match a test field.
2. The amounts required become the tristimulus values.
3. The observer is asked to name the colour being viewed.
Your Answer : (Not Answered)
Correct Answer : A
The first two are correct and describe the method. The third describes a naming task, which is quite different and far less reproducible. Matching is a far more reliable task than naming. Reproducibility is what makes the method useful.
Consider the following statements about maintaining a viewing cabinet.
1. Lamp hours are recorded and lamps replaced on schedule.
2. The interior surfaces must remain a specified neutral grey.
3. Lamps need replacing only when they fail to light at all.
Your Answer : (Not Answered)
Correct Answer : C
The first two are correct and are standard maintenance practice. The third would allow the assessment condition to drift far outside specification long before failure. Scheduled replacement is the only reliable method.
Which of these correlated colour temperatures would be described as the warmest in appearance?
Your Answer : (Not Answered)
Correct Answer : C
Correct answer: 2700 kelvin
The scale runs opposite to intuition: low colour temperatures are warm and reddish, high ones cool and bluish. So 2700 K is the warmest here, corresponding to domestic tungsten or a warm white lamp, while 6500 K is a cool daylight white.
The colour temperature of a source is
Your Answer : (Not Answered)
Correct Answer : C
Correct answer: the temperature of the blackbody whose colour it matches
Colour temperature is a description of appearance rather than of the lamp itself: it names the blackbody whose chromaticity the source shares. Note the inversion that catches people out - a higher colour temperature means a bluer, cooler-looking light, and a lower one a warmer, redder light.
Assertion (A): A white paper still appears white in dim light.
Reason (R): Lightness is judged relative to the surround rather than in absolute terms.
Your Answer : (Not Answered)
Correct Answer : D
Correct answer: Both A and R are true, and R is the correct explanation of A
Both are true and the reason explains why. In dim light the paper sends far less light to the eye, so its brightness falls, but everything around it falls in the same proportion; lightness, being the ratio, is unchanged. The visual system judges surfaces against their surround rather than absolutely, and that is what makes surface colours stable across a wide range of illumination.
Marks
Total number of questions : 20
Number of answered questions : 0
Number of unanswered questions : 20