HunterLab SpectraTrend HT, Руководство пользователя

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SpectraTrend HT User’s Guide 3.2
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APPENDIX A: MEASUREMENT VALUES
Color values measured using the SpectraTrend HT are relative to the absolute value or a perfect
reflecting diffuser as measured under the same geometric conditions (see ASTM E308), according to the
January 1, 1969 recommendation of the International Commission on Illumination, CIE.
This chapter explains the various color scales, color difference scales, and indices available for use.
Note: Not all of the indices or components of a color scale will be available on a single-
channel SpectraTrend HT.
Color Scales and Related Color Difference Scales and Indices
CIE Tristimulus XYZ Scale
The SpectraTrend HT performs integration of reflectance values over the visible spectrum to arrive at
tristimulus X, Y, and Z values. These values simulate the color matching response functions of the human
observer as defined by the 1931 2° Standard Observer or the 1964 CIE 10° Standard Observer.
Tristimulus integrations based on any of the illuminants listed on the next page may be performed. For a
complete description of how to calculate tristimulus values, refer to the publication CIE 15.2 and to
ASTM E308.
CIE Chromaticity Coordinates
The relationship between CIE XYZ and the x, y, chromaticity coordinates is as follows: , Yxy
Y = CIE Tristimulus Y
Z + Y X
X
= x
+
Z + Y + X
Y
= y
.
Opponent-Color Scales (Hunter Lab, CIE 1976 L*a*b*, and CIE L*C*h
The opponent-color scales yield measurements of color in units of approximate visual uniformity
throughout color space.
)
In the Hunter L, a, b scale, L measures lightness and varies from 100 for perfect white to zero for black,
approximately as the eye would evaluate it. The chromaticity dimensions (a and b) yield understandable
designations of color as follows:
a -- describes redness when positive, gray when zero, and greenness when negative.
b -- describes yellowness when positive, gray when zero, and blueness when negative.
The relationship between the Hunter L, a, b scale and the CIE XYZ scale for the CIE 1931 2° Standard
Observer and the CIE 1964 10° Standard Observer is as follows: