HunterLab SpectraTrend HT, User Manual

Page: 104 / 109

SpectraTrend HT User’s Guide 3.2
104
Where, L*, C*, and H* are those of the standard unless otherwise specified.
0.01765L + 1
* 0.040975L
= SL
for L* > 16
SL = 0.511 for L* < 16
SC =
0.0638C *
+ 0.0131C *
+ 0.638
1
SH = (FT + 1 - F) SC
2 2
* b * a * C
+ =
h = arctan
b *
a *





dL* = L*
SMP
- L*
STD
dC* = C*
SMP
- C*
STD
2 2 2
* dC * dL * dE = * dH
− −
1900 * C
* C
F
4
4
+
=
T = 0.36 + |0.4 cos (35 + h)| for h < 164° or h > 345°
T = 0.56 + |0.2 cos (168 + h)| for 164° < h < 345°
Tolerances are:
dL* = (cf) l SL dLc = cf
dC* = (cf) cSC dCc = cf
dH* = (cf) SH dHc = cf
dEc = cf
For a more detailed description of CMC, refer to “Calculation of Small Color Differences for
Acceptabilit y,” AATCC Test Method 173 -1992, published in the AATCC Technical Manual.
Gray Change
Gray Change indicates the amount of fading or color alteration that occurs with environmental exposure
or washing of textiles. The loss of color using the Gray Change Scale is evaluated by comparison to five
pairs of gray standards like those shown below. One half of each standard is always of identical chroma
to the starting specimen. The second half ranges from the starting chroma (no loss of color) to white
(loss of all color). The amount of contrast between the treated and untreated fabric is related to one of
the standard pairs to yield the gray scale rating. On this scale, 5 indicates that next to no color was lost,
and 1 indicates that most color was lost.