Secondary effects: Shutter speed

The secondary effect with the easiest of the three to understand is probably the shutter speed.

  • A fast shutter speed can freeze action.
  • A slow shutter speed will blur motion.

If you are shooting sports, chances are you are going to want to freeze their motion. To freeze motions that a person can do, your shutter speed needs to be at least 1/640 second. This will freeze a scene with small human motions in it, for example, a jogger or a friendly game of Ping-Pong. Faster shutter speeds will freeze quicker motion, for example, the moving arm of a baseball pitcher or a sprinter.

If you are shooting a waterfall, chances are you are going to want to let the motion of the water blur out a little bit. ½ second is a little bit of blur; an exposure of several seconds will turn moving water into a misty, creamy blob.

There is a down side to this secondary effect: Camera motion. Generally, one wants the camera to be perfectly still during an exposure. For example, the camera in this waterfall picture had to have been secured to a good, solid tripod during the exposure. Here is an image grabbed from the Internet that shows what camera motion blur looks like.

There are several technical ways to avoid camera shake.

  1. Use a high shutter speed. The rule of thumb is to use a shutter speed whose denominator is greater than the focal length in millimeters. That is, for a 100mm lens, shoot at 1/100 second or faster.
  2. Use a tripod.
  3. Use “image stabilization” (as it is called in the Canon world; also known as “vibration reduction” (Nikon) and “optical steady shot” (Sony)).

Next: Secondary effect: ISO