Critical fusion frequency as a function of stimulus intensity: and wavelength composition

Critical fusion frequency (CFF) values for a white and three colored targets were obtained on five Ss over a wide range of scotopic and photopic luminance levels. All the target:intensity values were taken from a decibel (dB) scale of luminance whose reference level was set at 10−10 L [10−6 trolands (Tr)] of white light. The major findings indicated that (a) the obtained curves relating CFF and stimulus intensity showed discontinuities at about 47 dB (.05 Tr), the approximate value of the photopic threshold, and (b) the CFF-intensity functions for the white and colored stimuli: were coincident above the photopic threshold, while in the scotopic range the blue curve exhibited marked lateral displacement over decreasing luminance values, the red function showed no displacement from the photopic functions, and the green and white curves were intermediate between those for blue hundred. The results were compared, on the same intensity scale with the findings of two other CFF studies and with recent reaction time research which provided similar support for the predictions of the duplicity theory of vision.