HunterLab EasyMatch QC, User Manual

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EasyMatch QC User’s Manual Version 2.1
Measurement Values A-31
Coefficient C/2° D65/2° C/10° D65/10°
C
X
1.2769 1.2985 1.2871 1.3013
C
Z
1.0592 1.1335 1.0781 1.1498
YI E313 Difference is also available, and is defined as follows:
dYI E313 = (YI E313)
sample
- (YI E313)
standard.
Yellowness Index per ASTM Method D1925 is calculated by the software as follows:
( )
Y
Z 8 1.05839817 - 5X 1.27497679 100
= D1925 YI under C/2° conditions for all instruments
except UltraScan XE.
( )
Y
Z 2 1.05743409 - 6X 1.27464150 100
= D1925 YI under C/2° conditions for UltraScan XE.
The yellowness index formula is shown in ASTM D1925 as:
( )
YI D1925 =
100 1.28 X - 1.06 Z
Y
CIE CIE
CIE
under C/2° conditions.
The tristimulus values of clear air (for CIE illuminant C and the 1931 CIE 2° standard observer) are X =
98.041, Y = 100.000, Z = 118.103. Using these values, the ASTM formula yields YI = 0.303 for clear
air because the factors are truncated to three significant figures. In order to set the yellowness index for
air equal to 0.0, the constant multipliers for X
CIE
and Z
CIE
have been expanded slightly.
The ASTM D1925 method was withdrawn in 1995, but this formula still provides useful information.
This index is always calculated for C/2°, regardless what illuminant and observer are chosen.
YI D1925 Difference is also available, and is defined as follows:
dYI D1925 = (YI D1925)
sample
- (YI D1925)
standard.
Paper Brightness (Z%)
Paper brightness, Z%, is used in the evaluation of the degradation of white materials. It can also be a
measure of the effectiveness of bleaching.
Z% =
100Z
Z
CIE
n
.
Z% Difference is also available, and is defined as follows:
dZ% = (Z%)
sample
- (Z%)
standard.