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The results of measurements of the critical flicker frequency of the eye depending on both the average luminance of the test field and the time function of this luminance were recorded by plotting the “ripple ratio” r versus the critical frequency; r is defined as amplitude of first Fourier component/average luminance of the stimulus. It is shown that with constant average luminance the points observed for various time functions fit into one smooth curve which for low luminances is monotonous.At high luminances the curve shows a minimum for r, which is smaller than the threshold value of the foveal brightness discrimination ratio 1.35 percent, observed for a frequency f = 1 c/s.
H. de Lange Dzn (Sat,) studied this question.