ABSTRACT
This chapter examines the limitations of the first visual transformation by considering the trade-off made between two very important requirements of an eye intended to operate efficiently within a particular range of light intensities: sufficient sensitivity to the available light and adequate resolution of spatial information inherent in that light. It discusses how adaptation provides a second, dynamic, determinant of the trade-off between resolution and sensitivity. The chapter also discusses the trade-off between resolution and sensitivity in compound eyes from two perspectives. Apposition eyes are common both in insects and crustaceans, and are especially common in those which are diurnal. In the most common type of apposition eye, the focal type, parallel light rays from a point source are focused by the axial corneal facet lens onto the distal tip of the rhabdom, which is looking in the direction from which the light is incident.
