A fair number of physical and biological limits of human vision will be reviewed and related to recent insights in the mechanisms of visual behaviour and perception.

(a) Physical limits and laws determine the optical and mechanical properties of our eyes and the kind of visual information available in our environment (ecological physics). (b) The information formats to which the visual system became tuned during evolution determine a functional architecture that is arbitrary from a physical or engineering perspective (many altemative solutions imaginable). However, the resulting system is meaningful biologically and based on the limits set by biological material (proteins) and coding (DNA, neural coding), phylogenetic incidents and the like. Of particular interest are the resulting neuronal processing principles and plasticity. (c) The actual (principled and incidental) mechanisms and limits of vision are nowadays studied more intensively than ever and with interesting results. It appears that our visual system sorts dynamical visual image information according to categories that are not a priori evident and it processes these ‘pieces’ of information in separate nuclei and cortical areas. The consequences of this fractionation principle are noticeable if lesions in one or more of these specialised brain regions lead to curious syndromes like face blindness (prosopagnosia), motion blindness, blindsight, visual agnosia, achromatopsia, a loss of local sign information (certain forms of amblyopia), etc. The mechanisms and limits of normal vision should be known in detail to understand pathologies, play with nervous plasticity or offer alternative visual cues and thus contribute to rehabilitation.