Transformations from cone responses to opponent color spaces

We have described a number of transformations by mapping the cone signal vector C, formed by LMS, to opponent space O, formed by achromatic signal OA, red-green signal Org, and yellow-blue signal Oyb. Two new transformations, Gop1 and Gop2, are proposed, based on the CIE 2006 spectral luminous efficiency function, VFo.THORN, and Hurvich's opponent spectral redgreen and yellow-blue responses, Hrgo.THORN and Hybo.THORN, without and with constraints, respectively. Gop1 is better than Gop2 in terms of best fit of Hrgo.THORN and Hybo.THORN, and both transformations improved previously proposed ones. Finally, we discuss the neutral conditions in cone space using each of the new and some of the extant transformations, as well as choosing scaling factors so that the neutral conditions in cone space are satisfied.