HunterLab SpectraTrend HT, User Manual

Page: 106 / 109

SpectraTrend HT User’s Guide 3.2
106
h =
h h
+ 180
M
abT abO
+
2
if |h
abT
- h
abO
| > 180 and |h
abT
+ h
abO
| < 360
h =
h h
- 180
M
abT abO
+
2
if |h
abT
- h
abO
| > 180 and |h
abT
+ h
abO
|

360
L*
T
, C*
abT
, h
abT
= lightness, chroma, and hue of Test specimen
L*
O
, C*
abO
, h
abO
= lightness, chroma, and hue of Original
dL* = L*
T
- L*
O
dC*
ab
= C*
abT
- C*
abO
sign of

H*
ab
= sign of (h
abT
- h
abO
)
2
ab
2
2
ab ab
* C * L * E = * H d d d d
− −
2 2 2
ab
* b + * a * L = * E d d d d
+
dE
F
is used to calculate Gray Change using the equations below:
1.7
dE
- 5 C GS
F
=
if dE
F

3.4
( )
2 log
0.85
dE
log
- 5 = C GS
F






if dE
F
> 3.4.
Gray Stain
The transference of color from the test specimen to an adjacent specimen is evaluated in a manner very
similar to that of Gray Change. Again, five standard pairs are used. One half of each standard is white,
and the second half range ranges from white (no staining) to a gray with the chroma value of the test
specimen (great deal of staining). A value of 5 corresponds to virtually no staining, whereas 1 indicates
poor color fastness
.
Gray Stain, as implemented, is based on ISO 105-A04:1989, Textiles- Tests for Colour Fastness - Part A04:
Method for the Instrumental Assessment of the Degree of Staining of Adjacent Fabrics. It is intended as
an alternative to visual assessment as described in ISO 105-A03: 1993, Textiles - Tests for Colour
The bottom half of
each pair shows the
starting color of the
adjacent fabric. The
top half shows the
color of the treated
adjacent fabric.
(Illustration from
AATCC Evaluation
Procedure 2).