The performance of eyes is ultimately limited by the physical nature of light. Diffraction in the lens aperture sets an upper limit to the spatial frequencies that can be imaged behind the aperture. In addition, the array of pixels the eye uses to detect an image is limited by the quantum nature of light. Each pixel can only detect a finite number of quanta, and any such count is associated with an uncertainty. Effectively, this limits the ability to detect differences in luminance (contrasts) across the image. Diffraction and quantum noise together sets an upper physical limit to the performance of an eye.
Because eyes are known to operate close to the physical limits, it is possible to predict the consequences of eye design and eye size under different luminance conditions and detection tasks. This provides a strong basis for theoretical visual ecology, through which we can understand the evolution and tuning of visual systems in animals. Some questions we are currently working on are:
1. Why do deep-sea squid have the largest eyes among all animals?
2. What are the relative merits of compound eyes and camera type eyes in bright and dim light?
Using similar theory we also investigate the consequences of crescent-shaped or W-shaped pupils in the eyes of ungulates, benthic fish and cephalopods.