A study of grating contrast judgement

Subjects judged the contrast of sinewave and narrow-bandwidth random gratings. The apparent contrast of gratings formed by summing two component gratings widely separated in frequency is independent of the relative phase of the component gratings and is equal to a linear sum of the subjective contrasts of the components when presented separately. A model is proposed in which the perceived contrast is formed by a linear sum of the outputs of multiple nonlinear channels.