How do I get descriptive colour differences?
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How do I get descriptive colour differences? |
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The L* C*ab H*ab representation is useful if qualitative colour differences are required. Differences can be calculated thus:
DL* = L*t - L*s,
DC*= C*t - C*s
DH*= {(Da*)2 + (Db*)2 - (DC*)2}1/2
where the subscripts s and b refer to standard and trial respectively.
If DL* is positive the trial is lighter than the standard, but if DL* is negative the trial is darker than the standard.
If DC* is positive the trial is stronger than the standard, but if DC* is negative the trial is weaker than the standard.
The hue descriptor is more difficult to determine: the radial direction in hue from the standard to the trial is used to give two hue descriptors (eg: redder/yellower): the descriptors are derived from the first two axes that are crossed in the a*-b* plane of colour space when moving from the standard to the trial in the direction of hue.