THE DESIGN AND USE OF A CONE CHROMATICITY SPACE - A TUTORIAL

Colorimetric data as revised by Judd can be transformed to Konig funda mentals L, M, S, representative of the long-(LWS), middle-(MWS), and s hort-(SWS) wave-length sensitive cone spectral sensitivities. The fund amentals are normalized so that two cone types, M and L, sum to the lu minous efficiency function, Y-J. The height of the S fundamental is un defined in this transformation. A constant luminance chromaticity plan e can be derived by calculating L/Y-J and S/Y-J, with the area of S se t equal to that of Y-J. This chromaticity space is convenient for calc ulations of real stimuli. The axes of this space, when adjusted to ref lect cone adaptation to the equal-energy spectrum have been shown to m atch the null axes of the major retino-cortical processing streams. Th e relative cone troland chromaticities can be multiplied by the retina l illuminance level to give L, M, and S trolands. In this metric, chro maticity data can be plotted as threshold-vs.-illuminance functions. C one excitation is derived from cone trolands, by dividing by the maxim al sensitivity of the fundamentals. Cone excitation units are used to derive models of retinal processing. The cone quantal excitation rate is a scaled version of the cone excitation. (C) 1996 John Wiley & Sons , Inc.