Mean data from 2 protanopes and 4 deuteranopes.
Data are in quantal units, normalized to peak at 0. They are 17 Hz flicker detection thresholds for 2-deg targets of variable wavelength presented in the center of a background field that alternated in color at 0.5 Hz. A violet background suppressed the S-cones. For details see Stockman, MacLeod & Johnson (1993).
Stockman, A., MacLeod, D. I. A. & Johnson, N. E. (1993). Spectral sensitivities of human cones. Journal of the Optical Society of America A, 10, 2491-2521.