The CMC ratio most commonly used for acceptability judgements in textiles is
Answer: C
It reflects the observation that lightness differences are better tolerated commercially. The one to one ratio is used where the question is whether a difference is visible at all. Two to one suits commercial acceptability instead.
Please log in or register to report this question.
Assertion (A): Different CMC ratios are appropriate for different questions.
Reason (R): Acceptability and perceptibility are distinct judgements with different weightings.
Answer: D
Both are true and the reason gives the distinction, and the ratio must be stated with the value. A CMC figure without its ratio is incomplete. The two ratios answer different questions. Acceptability and perceptibility differ in weighting.
Please log in or register to report this question.
Consider the following statements about acceptability and perceptibility.
1. Perceptibility asks whether a difference can be seen at all.
2. Acceptability asks whether it would be tolerated commercially.
3. The two questions always give the same answer.
Answer: A
Correct answer: 1 and 2 only
Statements 1 and 2 give the two distinct questions correctly. Statement 3 is the confusion the pairing exists to prevent: a difference may be plainly visible and entirely acceptable, or invisible in the laboratory and unacceptable when two pieces are laid side by side in daylight. Tolerances are set on acceptability, thresholds established on perceptibility.
Please log in or register to report this question.
A colour difference may be perceptible without being unacceptable because
Answer: B
Buyers accept differences they can see if the difference is small enough. Setting tolerances at the perceptibility threshold would reject most commercially satisfactory production. Buyers tolerate differences they can plainly see.
Please log in or register to report this question.
The CIE94 formula improves on Delta E ab by
Answer: C
Correct answer: applying weighting functions that increase with chroma
\( \Delta E^*_{ab} \) treats CIELAB as though it were perceptually uniform, which it is not - a given distance is far more visible near the neutral axis than out at high chroma. CIE94 divides the chroma and hue terms by weighting functions \( S_C \) and \( S_H \) that grow with chroma, so the acceptance region becomes an ellipse rather than a sphere.
Please log in or register to report this question.
Match each colour difference formula with its origin.
List I
A. Delta E ab
B. CMC
C. CIE94
D. CIEDE2000
List II
1. a CIE recommendation with chroma dependent weights
2. the simple Euclidean distance in CIELAB
3. the current CIE recommendation with a rotation term
4. the Colour Measurement Committee, for textiles
Answer: D
Each was an attempt to correct the non-uniformity of the underlying space. The later formulae were fitted to progressively larger sets of visual data. Each corrects the space a little further. Larger visual data sets underpin the later ones.
Please log in or register to report this question.
CIEDE2000 differs from CIE94 principally in adding
Answer: A
The rotation term corrects the tilted difference ellipses observed in the blue region. A revised lightness weighting and a chroma scaling for near neutral colours were also added. The rotation term is the most distinctive feature.
Please log in or register to report this question.
Assertion (A): The CIEDE2000 rotation term acts almost entirely in the blue region.
Reason (R): Experimental ellipses were found to be tilted only in that part of the space.
Answer: B
Both are true and the reason gives the empirical basis, and the term is negligible elsewhere. It is the most distinctive feature of the formula. It is negligible outside the blue region. Ellipse tilt was found only there.
Please log in or register to report this question.
Consider the following statements about CIEDE2000.
1. It includes a rotation term acting mainly in the blues.
2. It rescales chroma differences for near neutral colours.
3. It is a simple Euclidean distance like Delta E ab.
Answer: C
The first two are correct and describe its features. The third is quite wrong, since the formula is considerably more elaborate than a Euclidean distance. Several correction terms operate together. It is far from a simple distance calculation.
Please log in or register to report this question.
Parametric factors in a colour difference formula allow for
Answer: D
The formulae were fitted under defined conditions of illumination and presentation. Departures such as a separated pair or a textured sample are handled by these factors. The fitting assumed particular viewing conditions.
Please log in or register to report this question.
