This paper discusses about the most different illuminant (termed the orthogonal illuminant) compared with a reference illuminant. This is the first report on the definition of the orthogonal illuminant and on the solution of the optimization problem. As an application, the orthogonal illuminant is applied to counting metamers problem.
Nobuhito Matsushiro, Noboru Ohta, "Orthogonal Illuminant Model and Its Application to Counting Metamers" in Proc. IS&T 8th Color and Imaging Conf., 2000, pp 356 - 360, https://doi.org/10.2352/CIC.2000.8.1.art00063