Why do car wheels look as if they are spinning backwards on film?
Hi there. What you are seeing is a well known optical illusion that only occurs at certain speeds (in real life too, it is just easier to see on film – try it with a spinning top). As a wheel spins faster, it gets too fast for the eye to focus on – with persistence of vision (which is where the brain stores what it has already seen and builds on top of that base image) any spot on the wheel will appear first to stop still and then with an increase of speed will appear to go backwards. Simply put, the spot on the wheel you are attempting to focus on will not quite reach the same position in the time it takes your eye to notice it has moved – so it appears to go backwards. Cheers, Steve.
