Moving too fast

Something Phil Gyford wrote in his latest weeknotes struck a chord with me. Talking about the recent documentary about the Jonestown massacre, he said:

Unfortunately one mystery went entirely unexamined: why did the documentary makers stretch all the archive footage to the wrong aspect ratio? Maybe we’ll never know. Future generations will not only wonder why the people filmed in silent movies could move so quickly but why all the people filmed in the second half of the 20th century were so fat.

A good point. And it reminded me of something I was thinking recently watching whichever is the most recent big budget BBC nature documentary series. It featured (or if it didn’t, it made me think of it) footage of the Aurora (whether Australis or Borealis, I know not).

Footage of the aurora is usually sped up – I think. Certainly you often get weird swooshy effects when the shot contains humans or if there is any camera movement. I think it tends to be made up of multiple long exposures. As far as I know, the lights change and move quite slowly, and we are more used to seeing them move quite quickly.

I don’t think I always knew this was the case. I’ve never actually seen the aurora, so I can’t say for sure either way. But as far as I know, this is the case.

This is the same sort of phenomena as Phil mentioned above, where old footage is often herky-jerky or just plain too-fast, usually down to the way the camera was hand-cranked.

I’ve also never seen people from the first part of the 20th century walking around all fast and jerky, so I can’t say for sure etc. etc.

Anyway, it occurred to me, watching the BBC wildlife film, that some shots of animals are, inevitably, slowed down. Usually because what you’re seeing would happen far too quickly to see in real time. But it’s never really explained.

There must be a gland buried in our brains that tells us, usually due to contextual cues like other stuff in the frame: “That footage is slowed down because it must be.” Seeing foliage or water move similarly slowly nearby would be a hint. But it struck me that it’s never actually explained. We just sort of know it is. Unless some of us don’t.