Perception and visual acuity
Properties of human vision are central to image system engineering. They determine how many pixels need to be provided per degree of picture angle, and how many bits are necessary to represent luminance (or tristimulus) levels. This chapter introduces the luminance discrimination and spatial properties of vision that inform image system engineering choices.
The human retina has four types of photoreceptor cells that respond to incident radiation with different spectral response curves. A retina has about 100 million rod cells, effective only at extremely low light levels; and about 5 million cone cells, of three types, that mediate colour vision. Since there is only one type of rod cell, what is loosely ...