HunterLab SpectraTrend HT, User Manual

Page: 97 / 109

SpectraTrend HT User’s Guide 3.2
97
where:
3
n n
X
X
X
X
f
=






if X/X
n
> (24/116)
3
( )
116
16
+
X
X
108
841
=
X
X
f
n n












if X/X
n
≤ (24/116)
3
3
n n
Y
Y
Y
Y
f
=






if Y/Y
n
> (24/116)
3
( )
116
16
+
Y
Y
108
841
=
Y
Y
f
n n












if Y/Y
n
≤ (24/116)
3
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.
CIE L*C*h is a modification to the CIEL*a*b* scale, and plots in polar coordinates rather than
rectangular ones.
16 -
Y
Y
116 * L
3
n
=
C*
ab
=
2 2
* b * a
+
h° = arctan (b*/a*)
Reference: Commission Internationale de l’Elclairage (CIE): “Recommendations on Uniform Color
Spaces, Color Difference Equations, Psychometric Color Terms,“ Supplement no. 2 to CIE Publication No.
15, Colorimetry , Bureau Central de la CIE, Paris, 1978. For more information, see AATCC Test Method
173: Calculation of Small Color Differences .