Tritanopic purity-difference function to describe the properties of minimally distinct borders

Tansley and Boynton have recently demonstrated that color stimuli whose chromaticities all fall on a particular triptanopic confusion line in the CIE (x,y) diagram do not form distinct borders with each other. A tritanopic purity-difference function, involving only r- and g-cone contributions, is demonstrated to provide (i) a prediction of which chromatic stimuli have equivalent border-forming properties, and (ii) a description of the distinctness of minimally distinct borders (MDB) in terms of an equivalent luminance contrast. The tritanopic purity-difference concept is demonstrated to account for all available data on the assessment of the distinctness of borders at the MDB point.