Color Analysis Using Photovolt Reflectometers

description:

A spreadsheet application for Microsoft Excel, “PVI Color Conversion”  converts the amber, blue, and green reflectance measurements from the PHOTOVOLT MODEL 577 Reflectance Meters to CIE XYZ and to L*a*b* values. Values for yellowness, whiteness, total color difference (Delta “E”), and delta chromaticity (Delta “C”) are also calculated. A single report or a group format is available. A PHOTOVOLT “T” or “Y” search unit must be used and each unit must be equipped with tristimulus filters to measure amber, blue, and green percent reflectance.

installation of analysis program:

• Microsoft Excel for Windows, Version 3.0 or later

color coordinate formulas :

ABG%
• A = Percent reflectance value with the AMBER tristimulus filter
• B = Percent reflectance value with the BLUE tristimulus filter
• G = Percent reflectance value with the GREEN tristiumuus filter

CIE – X, Y, Z Scale
X = 0.80 A + 0.18 B
Y = 1.00 G
Z = 1.18 B
ASTM D 2244
ASTM D 2244
ASTM D 2244
L*a*b* (CIE 1976)
L* = 116 (Y/100)^1/3 – 16
a* = 500 ((X/100)^1/3 – (Y/100)^1/3)
b* = 200 ((Y/100) ^1/3 – (Z/100)^1/3)
ASTM D 2244
ASTM D 2244
ASTM D 2244
L* = 116 (Y/100) ^1/3 – 16
u’ = 4X/(X + 15Y + 3Z)
v’ = 9Y/(X + 15Y + 3Z)
ASTM D 2244
ASTM D 2244
ASTM D 2244
Simplified NBS Equation
L = 10 Y^½
a = (17.5 (1.02 X-Y)) / Y^½
b = (7.0 (Y – 0.847 Z)) / Y^½
ASTM D 2244
ASTM D 2244
ASTM D 2244
Yellowness Index
YI = 100 (A – B) / G
YI = 128X – 106Z / Y
YI = 100 (1 – 0.847 Z / Y)
ASTM E 313
ASTM D 1925
ASTM E 313
Whiteness Index
WI = 4 B – 3 G
ASTM E 313
Delta Values
d”E” of L*a*b** =
((L1*-L2*)^2+(a1*-a2*)^2+(b1*-b2*)^2)^½

d”E” of L a b =
((L1-L2)^2+(a1-a2)^2+(b1-b2)^2)^½

d”C” of a* b* = ((a1*-a2*)^2+(b1*-b2*)^2)^½

d”C” of a b = ((a1-a2)^2+(b1-b2)^2)^½

ASTM D 2244

ASTM D 2244

ASTM D 2244

ASTM D 2244

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