Shaking head wiggling effect

[colonelpanic]

Hi gurus,
I don't know what this effect is called but you can see it occasionally especially in spooky films or music videos.

It looks like somebody shaking his head at an incredibly high speed whereas the rest of the body and the background stay perfectly normal. There's also quite a bit of motion blur and other for me unidentifiable artifacts on and around the head.

I've been fiddling around with the wiggler in AE but it looks very crude. I'm struggling to make the head look like it's rotating from left to right on the vertical axis and, at the same time, keep everything else in the scene more or less normal.

It would be cool if somebody could just give me the proper term for this effect. I can then look it up.

Thanks

PS I remember having seen it in Saw1. The scene where that big bloke is tied up in a cage with barb wire and chops himself up with blades attached to his body.

[Fletch78]

One option would be: use a tripod, set a low (about 12 or lower) shutter speed and have the actor shake his head (doesn't have to be fast, you can speed it up later) while otherwise standing/sitting perfectly still.

[tcindie]

It certainly sounds like the result of some time remapping..

[colonelpanic]

Cheers mates. That could do the trick, definitely for the head part.

I wasn't really precise in my initial question. The idea is to have the talent walk down the street towards the camera, while the background and his body keep moving at normal speed.
I suppose my only option would be green screening and then cut out the (natural) head and somehow overlay the shaking head back on his shoulders in the walking scene.

Seems like it could become extremely tedious, unless there is a simpler way I can't think of now, perhaps some option in AE CS3 I'm not familiar with. In tutorials I sometimes see the tutor use certain functions whose names suggest something totally different from what he uses them for. That's when I think 'oh ok, that's what this thing can be used for...'

When I saw this effect I always had the impression that only part of the frame (the head or an arm) was sped up whereas other objects kept moving at normal speed. I'll see if I can find other examples. Maybe I was hallucinating...

Thanks

edit: another example is Jacob's Ladder. I found this clip on youtube, somebody trying to reproduce the effect. It's sort of close but still a bit crude and not yet what I'm after.
http://www.youtube.com/watch?v=yIgplO3LZWE&feature=related

I've read somewhere that the director of Jacob's Ladder, Adrian Lyne was the first to create this effect and achieved it by randomly cutting out frames from a shot at normal speed. I don't know about that one though. I'll try that when I have some time and keep you posted, for those interested.