HunterLab SpectraTrend HT, User Manual

Page: 102 / 109

SpectraTrend HT User’s Guide 3.2
102
dYIE and dYID
These indices yield the differences between the sample and the standard via the Yellowness Index E313
and Yellowness Index D1925.
dYIE = YIE
sample
- YIE
standard
dYID = YID
sample
- YID
standard
dZ%
This index yields the difference between the sample and the standard via the Z% index.
dZ% = Z%
sample
- Z%
standard
.
Other Indices (available with Absolute and Difference Display Types;
Reading of Both Standard and Sample Required)
dE Total Color Difference
The Hunter L, a, b total color difference for any illuminant and observer is calculated as follows:
2 2 2
db da dL = dE
+ +
.
dE approximates the NBS Unit of Color Difference (Judd-Hunter), which represents the average
maximum difference acceptable in a series of dye house commercial matches in 1939.
dC Chromaticity Difference
The Hunter L, a, b chromaticity difference for any illuminant and observer is calculated as follows:
2 2
db + da = dC
.
dE* Total Color Difference
CIE dE* total color difference is defined as follows:
2 2 2
* db + * da * dL = * dE
+
.
dC* Chroma Difference
CIE dC* chroma difference is defined as follows:
dC* = C*
sample
- C*
standard
where
2 2
* b * a * C
+ =
and is termed metric chroma.