AS NZS 1301.530:2016 Methods of test for pulp and paper- Determination of colour by diffuse reflectance
A.2.1 General
The desired tristimulus values are obtained by summing the products of the spectral reflectance factors and the weighting functions given in ASTM E3081) for the C illuminant and CIE 1931 (2°) observer.
“Checksum”and“white point” data are given at the bottom of each column in Tables A.1, A.2, A.3 and A.4. The“checksum” is the algebraic sum of the entries. It provides, for convenience, a check value to ensure that the tables have been copied correctly, should copying be required. These checksums may not be identical with the “white point” data located below them because of roundoff. Each value in a column has been rounded to three decimal digits. It is these“white point” data, and no other, that shall be used as Xn, Yn, Zn when converting tristimulus values calculated by use of these tables to CIELAB or CIELUV coordinates or for any other purpose requiring the ratio of the tristimulus value of the specimen to that of the“white point”.
Apply the following instructions, given in ASTM E308, when the values are not available at the top or at the bottom of the range.
Wavelength range less than 360 nm to 780 nm. When data for (λ) are not available for the full wavelength range, add the weights at the wavelengths for which data are not available to the weights at the shortest or longest wavelength for which spectral data are available, i.e.:
a) add the weights for all wavelengths (360 nm, .. for which measured data are not available to the next higher weight for which such data are available;
b) add the weights for all wavelengths (…. 780 nm) for which measured data are not available to the next lower weight for which such data are available.
In the absence of fluorescence, the spectral radiance factor can be replaced by, or referred to as, the spectral reflectance factor, R(2).