For a special purpose (a mock sixties film) I tried to emulate the posterized effect that was seen on some psychedelic films (the Monkee's "Head" intro for instance). So I tweaked some cursors on the Blender compositor to get the effect I was looking for. If anyone has better ideas for a polarized effect, I would be ready to use them
This is pretty cool, just started to use it but all can be keyframed in the nodes editor, it ends up working well to posterize a whole movie. Pretty cool, will definitely use it.