HunterLab EasyMatch QC, Руководство пользователя

Страница: 294 / 366

EasyMatch QC User’s Manual Version 2.1
A-4 Measurement Values
3
n n
Z
Z
Z
Z
f
=






if Z/Z
n
> (24/116)
3
( )
116
16
+
Z
Z
108
841
=
Z
Z
f
n n












if Z/Z
n
≤ (24/116)
3
and X
n
, Y
n
, and Z
n
are tristimulus values for any illuminant.
Total Difference (dE*), CIE 1976 a,b Chroma-Difference (dC*), and CIE 1976 a,b Hue Difference
(dH*) are defined as follows:
2 2 2
* db + * da * dL = * dE
+
dC* = C*
smp
- C*
std
where
2 2
* b * a * C
+ =
and is termed metric chroma
2 2 2
* dC * dL * dE = * dH
− −
where
dL* = L*
SMP
- L*
STD
da* = a*
SMP
- a*
STD
db* - b*
SMP
- b*
STD
For more information, see AATCC Test Method 173: Calculation of Small Color Differences .
CIE LCh is a modification to the CIELAB scale which plots in polar coordinates rather than rectangular
ones.
dC* is the difference between the chroma of the sample and the chroma of the standard, as described in
a polar coordinate system.
dh* describes the difference between the hue angle (h°) of the standard and the hue angle of the sample
in a polar coordinate system, where:
If h°smp > h°std then dh* is regarded as positive.
If h°std > h°smp then dh* is regarded as negative.
See “Recommendation on Uniform Color Spaces, Color Difference Equations, Psychometric Color
Terms,” Supplement No. 2 to
CIE Publication No. 15 (E-1.3.1) CIE, Paris, 1978.
L* = CIE 1976 psychometric lightness = 16 -
Y
Y
116
3
n
a* = Red(+) - Green(-) axis =








3
n
3
n
Y
Y
-
X
X
500