The batteries in our digital cameras and notebook computers constantly remind us that energy must be used to capture and process images. A retina is no exception. Work initiated in insect compound eyes reveals how eyes are designed to satisfy their hunger for information while keeping at bay their hunger for metabolic energy. These designs involve a number of operations that are commonplace in retinal physiology; adaptation to light level, intensity dependent receptive fields and response dynamics, signal amplification, gradations in spatial sampling across the retina, analogue signal processing and the division of information into parallel streams. This work was initiated by a collaboration that had its roots in the work of W.S. Stiles. Its findings demonstrates how the use of non-mammalian species can illuminate the function of our own eye by identifying design features that are so useful that no good eye can afford to work without them.