Corrected entry: In the scene where Snape takes over the Defense against the dark arts class, (about werewolves) when the projector changes slides, on the screen the image moves clockwise at the top. However, when you see the projector, the light enabling a picture to be projected is on the bottom and the slides rotate counter clockwise.
kevkevtheman
3rd Sep 2011
Correction: Many projectors flip the image, showing it on the screen upside down and backward to the film's orientation. This must be one of those projectors.
Phixius ★