Shutter speed measures the amount of time the camera’s shutter is open. The longer it is open, the more light can enter. Doubling or halving the shutter speed produces an increase or decrease of 1 stop of exposure. Fast shutter speeds freeze motion (e.g., a bird’s wings while flying) and slow shutter speeds blur motion (e.g., milky looking water fall). The exposure length is rounded some to make the math a little easier. For example, whole stop values are 1/1000 s, 1/500 s, 1/250 s, 1/125 s, 1/60 s, 1/30 s, 1/15 s, 1/8 s, 1/4 s, 1/2 s, 1 s, 2 s… The inverse of the values are typically selected on your camera (i.e., 1000, 500, 250, 125, 60, 30, 15, 8, 4, 2…) for values less than 1 s. For values greater than or equal to 1 s a double prime symbol is used after the value (i.e., 1″, 2″, 4″, 8″…).
For most bird photographs, the shutter speed typically is between 1/60 to 1/2000 second (s). Why such a large range? If you are taking a photograph of a dove sitting on a branch you can use a much slower speed – it doesn’t move much. If you want to freeze the wings of a hummingbird you need a very fast speed.
The shutter speed is also limited by the focal length of the lens attached to the camera. For a full frame camera, the shutter speed should be no slower than 1/focal length. So, a 500 mm lens should have a shutter speed of no slower than 1/500 second. Fortunately, many lenses have vibration reduction which will permit a slower shutter speed. For example, if the 500 mm lens had 3 stops of vibration reduction, the slowest shutter speed could be reduced to 1/60 second. As discussed in a future post, cropped sensor lenses have an effective focal length. So, when using those cameras, the shutter speed should be no slower than 1/effective focal length. This value may also be adjusted based on how many stops of vibration reduction are provided by the lens.