Dolly Zoom

Mosio demonstrated the different optical effects you get with lenses of different focal lengths. He showed us slides of his friend against a background, maintaining the same image size by moving back as he switched to longer focal lengths. A dolly zoom is the effect you get when you film this in real-time. It was most famously used in Hitchcock’s Vertigo.

Here’s another good example from The Fellowship of the Ring.

It’s a pretty groovy effect, but there’s a big danger of it looking cliche if used in the wrong way.

More info on the dolly zoom.