The first thing that comes to mind when I read this term is not necessarily the title of one of Michelangelo Antonioni's (see above) films. It is something bad happening to the motor of the vehicle one is using. Like this event below for example :
(image courtesy of the very creative Spanish site 8negro)
But then nothing is totally bad, is it?
The other sense is of course an enlarged photograph, which may, in some cases, reveal something that was not visible to the naked eye, like this one which provided one of the themes and the title for Antonioni's film made in the "swinging" London of the mid-late 1960's (which was indeed the other theme of this film). This was a time when I was a student in London and I remember it well.
Did the photographer really witness, unknowingly, a murder scene in the park?
The other main theme of Blow-Up was the superficial but attractive lifestyle of a fashion photographer in London at a time when open sexual (and insouciant nouveau-riche) behaviour was a relative novelty, and the world of fashion was also emerging from years of rigidity. When one sees this film today it seems very dated and, somehow, innocent. I am not too sure what today's 20 something year-olds would make of it.
I was both fascinated and, at times, bored by Antonioni's films. Maybe it is time to take another look. I was also quite fascinated by the actress Monica Vitti who played in many of his early films, although not in Blow Up.