HunterLab EasyMatch QC, Руководство пользователя

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EasyMatch QC User’s Manual Version 2.1
Measurement Values A-21
Excitation purity is the percentage contribution of the dominant wavelength to the mixture. Thus, 1.00
is the purity of all spectral colors and 0 is the purity of the illuminant. Excitation purity correlates with
saturation.
In order to derive dominant wavelength and excitation purity for a sample, plot the position of the
illuminant C - object color combination on the CIE x,y chromaticity diagram. The dominant wavelength
for sample (S) under illuminant C is found by drawing a straight line from the Illuminant C point
through S to the spectrum locus, where it intersects at the dominant wavelength. Excitation purity is the
percentage of the distance from illuminant C to S compared to the total distance from illuminant C to the
spectrum locus.
Dominant wavelength and excitation purity are calculated for the wavelengths of 397-673 nm. These
values are always calculated and displayed relative to the CIE 1931 2° standard observer and CIE
illuminant C regardless of the selected illuminant and observer. For complementary wavelengths, the
displayed values are less than zero.
For further information see “A Digital Computer Technique for Calculation of Dominant Wavelength”
by Charles G. Leete and Jack R. Lytle in
Color Engineering , Volume 4, No. 1 (January - February
1966).
Dominant Wavelength Difference and Excitation Purity Difference are also available, and are defined as
follows:
dDominant Wavelength = (Dominant Wavelength)
sample
- (Dominant Wavelength)
standard,
dExcitation Purity = (Excitation Purity)
sample
- (Excitation Purity)
standard.
EBC-10 mm (ColorQuest XE, ColorQuest XT, ColorQuest II Sphere,
UltraScan XE, UltraScan PRO, and UltraScan VIS only)
The European Brewing Chemists (EBC) scale is used in the measurement of color of beer, malt worts,
caramel solutions, and similarly-colored liquids. The range of this transmission scale is 2 to 27 units,
with yellower, pale worts at the low end and redder dark worts, beers, and caramels at the upper end. A
10-mm path length cell should be used for these measurements. EBC values are calculated as follows:
( )
nm 430 10
T log - * 25f EBC
=
where
f = EBC dilution factor (default = 1.0)
T
430 nm
= measured transmittance value (%) at 430 nm
and
Turbidity = free (“0.0”) if
( )
nm 430 10
nm 700
10
T log - * 1.27 * 0.039
100
T
log - * 1.27
≤






, else turbid (“1.0”).
where