Flicker fusion thresholds of red-green dichromats.

Measurements of the relative energies required for critical flicker fusion (CFF) at each of 14 wavelengths were obtained in normal, protanopic, and deuteranopic observers. Normals required more energy beyond 580 nm in going from 30 to 40 flashes per second than protanopes or deuteranopes. This suggests an adaptational collapse of the red-sensitive mechanism of normals which is not present in the red cones of deuteranopes or the green cones of protanopes over the same intensity range.