Consequences of spatial sampling by a human photoreceptor mosaic.

The short wavelength color mechanism in the human visual system can distinguish gratings from uniform fields of the same average radiance at spatial frequencies that are twice as high as the highest at which it can resolve bars in the grating. This discrimination above the resolution limit is associated with a splotchy or mottled appearance of the grating similar to two-dimensional noise. The most plausible explanation for the mottled pattern is that it is a moiré pattern produced by aliasing (spatial undersampling) by an irregular and sparse mosaic of short wavelength cones.