oooooooooooommmmmmmmmmgggggggggg lol i'm dying. I'm sorry man but damn.
A standard computer monitor refreshes its image 60 times per second.
When a game refreshes its image 60 times per second, the resultant video is smooth. Each 'image' is onscreen for exactly 1/60th of a second.
When a game refreshes its image 30 times per second, the image is also smooth. Because each individual 'image' is onscreen for exactly 'two' frames, or 2/60th of a second, evenly.
When a game refreshes its image 45 times per second on a screen that refreshes 60 times per second, the game must repeat every 3rd frame in each set of 3 frames. Meaning, 15 times every second, one 'image' will be onscreen twice as long as it should be. hence, judder, studder, whatever you call it.
For anyone who's interested,
play this video, fullscreen, at 1080/60. It's a video of Far Cry 3, locked at 45fps, played back at 60fps. The judder is pretty obvious. It's like trying to watch 1080p Youtube on a computer from 2003.