Pigments in anomalous trichromats

Abstract

Protanomalous and deuteranomalous subjects must have an abnormal cone pigment to account for their rejection of the normal Rayleigh equation (red + green = yellow). The technique of Exchange Thresholds was used to discover what it is. With the protanomalous, the red intensity was set so that a protanope could not detect the change from red to green. Thus detection by the protanomalous must be by action of his other kind of cone—the anomalous cone. The exchange lights were presented upon a steady background of either red or green light, and the red intensity was adjusted to raise the exchange threshold as much as the green did. Then anomalous cones absorb light equally from these two backgrounds. We set our Analytical Anomaloscope with this red/green ratio, and made Rayleigh matches with lights of various wave lengths. With this setting, the energy E λ of each matching light is inversely as the spectral sensitivity of the anomalous pigment at λ. The protanomalous pigment curve has the shape expected of a visual pigment with peak at about 550 nm. The deuteranomalous pigment has its peak at about 555 nm.