HunterLab EasyMatch QC, User Manual

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EasyMatch QC User’s Manual Version 2.1
A-20 Measurement Values
Color Value SWL
Color Value SWL is the K/S measured at the wavelength of maximum absorption (minimum reflection)
for reflectance measurements or the absorbance at the wavelength of maximum absorption (minimum
transmittance) for transmittance measurements. K/S and Absorbance are described in the Spectral Data
Types section of this appendix.
Color Value SWL Difference is also available, and is defined as follows:
dColor Value SWL = (Color Value SWL)
sample
- (Color Value SWL)
standard.
Color Value WSUM
Color Value WSUM is calculated using the sum of K/S weighted by illuminant and observer for the
sample read the spectrum for reflectance measurements, and using the sum of absorbances weighted by
illuminant and observer for the sample read across the spectrum for transmittance measurements.
points #
S * E *
S
K
= WSUM Value Color
points #
1 =
∑
λ
λ λ
λ
for reflectance
points #
S * E * Absorbance
= WSUM Value Color
points #
1 =
∑
λ
λ λ λ
for transmittance
where E = Energy distribution of light source
S = Observer function.
K/S and Absorbance are described in the Spectral Data Types section of this appendix.
Color Value WSUM Difference is also available, and is defined as follows:
dColor Value WSUM = (Color Value WSUM)
sample
- (Color Value WSUM)
standard.
Dominant WaveLength and Excitation Purity
The dominant wavelength and excitation purity chromaticity system was one of the first systems for
specifying the chromaticity of objects other than by their x, y values. It not only compensates for the
influence of the illuminant’s chromaticity, but also improves the correlation between the numbers and
visual attributes because it permits chromaticity specification in terms of hue and saturation. The system
is based on the additive-color-mixing properties of the x,y diagram. A color is specified by describing
how it would be matched by additively mixing the illuminant and light of some single wavelengths.
Dominant wavelength is the wavelength needed for mixture with the illuminant. In general, it identifies
the hue of the object’s color.