Relationship of the threshold contrast of visual stimuli in the photopic, mesopic, and scotopic ranges of luminance

Using a model to predict the probability of discriminating visual stimuli, their threshold contrasts are calculated in wide ranges of the angular size of the stimulus and the adaptation luminance of vision. It is established that the calculated parameters at the limiting luminance of the mesopic range determine the threshold contrast of the stimulus in the photopic and scotopic ranges of adaptation luminance, respectively. The results of the calculation agree with the data of Blackwell’s well-known experiment.