Campbell and Robson Found That, as Their Contrasts Were Increased

Multiple Choice

Campbell and Robson found that, as their contrasts were increased, a low contrast square-wave grating could be discriminated from a low contrast sine-wave grating when:

A) The fifth harmonic of the square-wave grating reached its contrast threshold
B) Both gratings reached 20% contrast
C) The third harmonic of the square-wave grating reached its contrast threshold
D) Only if spatial frequency was lower than 2 c deg⁻¹