Thursday, May 17, 2007
Technique: Adjusting Scan Rate for Cool (or Practical) Anti-Strobing Effect
The video above is an awesome example of a practical in-camera effect you can get by messing with your cam's manual settings. In this example, the helicopter's blades appear to be stationary because the film camera is set at a frame speed that matches the rotor speed (notice the tail rotor still appears to spin slowly). This same basic effect happens in the human eye when the spokes of a moving bike or rims of moving car appear to spin backward.
In the low budget world, this effect is impossible. You could adjust the video scan rate on a high-end camera, I suppose, but who has access to such a camera, and what purpose would it serve? A cool gimmick perhaps, but not one most of us have a use for.
The best purpose for this type of effect is probably the reverse of how it is applied here. When shooting computer monitors, they will typically appear to strobe, or have nasty black lines through them. This is due to the non-matching scan rates on both camera and monitor. Since you can't (in most cases) adjust the camera, adjust the monitor instead. Setting the monitor's refresh rate to 60 Hertz should take care of the problem.