Roger wrote:
Theory on timing...
These cameras still use real film don't they? This has to be wound on. Supposing that some film has a maximum wind rate a bit lower than other - or maybe the rate has to be slowed down when the film is cold? That would mean a change of timing (or a general lengthening overall) Perhaps they're using so much film that they can save money by not having the fast-wind stuff?
They're effectively shooting at about 1.5 to 2 frames per second, and the lower end isn't much faster than a good photographer could shoot a manual wind SLR. They buy film in bulk lengths of 100 foot, which is about the cheapest way anyone can lay their mitts on 35mm film stock. They always shoot two frames for each offence, so the only way they can cut costs is to photograph fewer cars. Film's so cheap I doubt it's a concern.
Different films won't have much variation in the speed at which you can wind them on. I suppose there's a theoretical top wind-on speed, but even pro spec bodies are nowhere near it at speeds of 7 or 8 fps, never mind 2 fps in a Gatso. Movie cameras use 35mm stock too, and they go a hell of a lot faster. It isn't the film that limits wind-on speed in practice, it's the type of camera.
If it's really really hot the emulsion might start getting sticky and gumming things up, but that would probably apply to all film fairly evenly. And celluloid burns of course. Probably never gets hot enough in the UK for it to be a problem. Cold shouldn't have any effect at all. I keep film in the fridge, and the only caveat is to let it get to the same temperature as the camera before you load it. After that it really doesn't matter how cold it gets. People have taken stunning photos on top of Everest and at both poles with film cameras. The batteries snuff it a lot faster than normal, but the film isn't a problem.