Recent progress in computing weighting tables for calculating CIE tristimulus values

Abstract

In industrial practice, it is often required that weighting tables were prepared in advance and tristimulus values can then be directly computed using summation of the products of the weights and measured reflectance values. The CIE has never provided precise procedure to calculate the weighting tables, and various discrepant methods have been used. Hence it is possible to obtain significantly different tristimulus values from the same set of spectral data.

Testing the accuracy of methods for the computation of CIE tristimulus values using weighting tables

“…The LWL and LLR methods were introduced above. There are many other methods that can be used to compute TSVs including the ASTM weighting tables, the CIE recommendations, the Oleari methods, and the Direct Selection method . These will be briefly introduced in this section, before the performance of all the different methods is compared.…”

“…can be used. The use of 1 nm data can be considered as a reference procedure for the computation of TSVs: it was termed the CIE‐R method by Li …”

“…In 2000, Oleari developed a method for computing TSVs based on local power expansion for the product of the CMFs and SPD of the illuminant. In 2005, the least squares method for computing TSVs was introduced and recently, Li et al . have described methods for computing zero‐ and second‐order weighting tables based on the Oleari method .…”

“…have described methods for computing zero‐ and second‐order weighting tables based on the Oleari method . In summary, various approaches have been used or proposed for the computation of TSVs, the undesirable fact being that they can each lead to different results when starting from the same set of measured spectral data . Hence, there is a strong need for a unified method for the accurate computation of TSVs from spectral reflectance data at intervals greater than 1 nm, for example, to provide the best agreement between laboratories.…”

“…The least squares method was introduced during the 10th Congress of the International Colour Association (AIC) by Wang et al . and the 20th Congress of the International Commission for Optics (ICO‐20) by Li et al . and, from the names of its co‐authors, the method will be termed the Li–Wang–Luo (LWL) method.…”