3.3. Human Visual System   

Since computer images are seen by the eye, it is important to know what is special about human vision. Most people have good colour and spatial resolution - they can see the correct colours and features in a scene.

intensity threshold: the intensity increase needed to be perceived is proportional to the illumination of the scene.

animation: a series of images becomes animated (i.e. seen to be continuous rather than discrete) at the fusion point (~~ 50 images/second).

rods and cones: the eye contains two types of receptors - rods (high spatial black and white receptors) and cones (colour receptors).

detection: the eye can detect as little as a few photons.

spatial discontinuities: the eye is very good at detecting discontinuous edges (hence the very annoying jaggies of non anti-aliased images).