I was really looking forward to giving this lecture on Computer Vision. After all, this is the field I work in. Actually it was much trickier than I expected -- if you know quite a bit about something it is much more difficult to be concise! Anyway, give it a go, see what you think.
Incidentally, I have illustrated this post with a famous picture known as "Atteneave's cat"" [1]. The interesting thing about Atteneave's cat is the amount of semantic information (a sleeping cat) carried in only 64 straight lines. This is one example of the pyramidal structure of vision: vast amounts of pixel data can be summarised with very compact descriptions.
Fred Attneave, Some information aspects of visual attention, Pyschololical Review 61 (3), 1954, pp 183--193.