HunterLab EasyMatch QC, User Manual

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EasyMatch QC User’s Manual Version 2.1
A-28 Measurement Values
Whiteness Index per CIE is equivalent to the whiteness index published in ASTM Method E313 .
WI CIE = Y + 800 (x
n
- x) + 1700 (y
n
- y) = WI E313
where Y, x, y are the luminance factor and chromaticity coordinates of the specimen, and x
n
and y
n
are
the chromaticity coordinates for the CIE standard illuminant and source used. These values are provided
in the table below based on the illuminant and observer used. Whiteness Index can only be calculated
for illuminants C, D50, and D65. A blank cell is received when any other illuminant is in use.
Value C/2° D50/2° D65/2° C/10° D50/10° D65/10°
x
n
0.3101 0.3457 0.3127 0.3104 0.3477 0.3138
y
n
0.3161 0.3585 0.3290 0.3191 0.3595 0.3310
Refer to ASTM Method E313, “Standard Practice for Calculating Yellowness and Whiteness Indices
from Instrumentally Measured Color Coordinates,” for more information.
Whiteness Index per the CIE Colorimetry Committee (displayed as Whiteness Index CIE) is the same as
the current ASTM E313 whiteness described above, but may only be calculated and displayed for
D65/2°, D65/10°, and C/2°. The CIE method on which this index is based is equivalent to AATCC Test
Method 110: Whiteness of Textiles.
WI CIE Difference and WI E313 Difference are also available, and are defined as follows:
dWI CIE = (WI CIE)
sample
- (WI CIE)
standard,
dWI E313 = (WI E313)
sample
- (WI E313)
standard.
Spectral reflectance can vary based on the geometry of the instrument used, the exact properties of the
illuminant simulated (usually D65), and the condition of the instrument’s lamp. This can be a problem,
especially for measurement of fluorescent samples, where maintenance of a constant illuminant spectral
energy distribution is imperative. The main purpose in creating the
Ganz Whiteness Index was to
allow constant, comparable results for whiteness and tint of fluorescent materials, even by using
instruments of different designs and different illuminant simulation.
WI GANZ = DY + Px + Qy + C for D65/10°
where
D =
W
Y
= 1
δ
δ
( )
( )












ϕ
η ϕ
δ
δ
cos
+ cos
*
S
W -
= P = -1868.322 for UltraScan XE
= a similar value, optimized for each individual instrument for
ColorQuest XE, LabScan XE, UltraScan PRO, and UltraScan VIS