What shutter speed to use when shooting video?

Question

My camera is Canon 60D and I will be using it to shoot a short parkour video, that means:

• a lot of motion, moving subjects, moving camera
• focal length usually from 24 mm to 75 mm, but there will also be a scenes shot at 200 mm
• a lot will be shot in 1080 at 24 fps (or should I use 25 fps or 30 fps ?)
• some scenes will be shot in 720 at 60 fps

Accessories:

• I do have a steadicam
• I have got 1.8 lenses (24 f/1.8, 35 f/1.8, 50 f/1.8) so I can use low f-stops.

Questions:

• What shutter speed should I use? I have read that it should be double the FPS. Why so? What if I break this rule?
• When I use low shutter speeds (1/120) and I'm shooting during the day, I need f-stop at around f/12. Does this mean that my f/1.8 lens are useless in this case and I can use any bundle f/4 lenses instead?
• Any tips on improving whatever I wrote above?

Answer

The reason that many people will recommend to shoot at double your framerate is because then the 'shutter angle' is 180 degrees.

This is back from when film cameras were used. To cover the negatives whilst the next frame was 'wound on', a disc would spin, blocking the light as the negative moved. When the negative was in place, this disc would spin open again. Wikipedia has a good animation of this here.

The amount of covering the disc provides and the framerate give this 180 degrees that is as close as you get to a 'standard' in filmmaking. For further reading on this (or a better explanation!) I'd suggest looking over here.

As for a specific recommendation of shutter speed, it depends on the look you want. For example, some action films (using these as an example because they have lots of movement within the frame) will use a very fast shutter speed for sharp images, but being professional films they are still shooting at a framerate (or 23.976). Others will use the slowest they can get away with, and this will give them lots of motion blur within the shot. A good film that shows examples of both of these is The Bourne Identity.

TL;DR - It's a creative decision.

As for the problem with your F-stops, this is (unfortunately, because you have some real nice lenses) just something you're going to have to live with. Consider whether a slow shutter speed is absolutely necessary for these scenes. Using a faster one could allow you to use your f1.8. Also, depending on the camera you're shooting on, sometimes setting it to 'Auto ISO' can actually let the camera reduce the ISO below the minimum (100, normally) using some metadata hacks or something. (This may just be for stills, though!)

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