What is shutter speed?
Slow Shutter Speed
Fast Shutter Speed
Shutter speed is the amount of time that the shutter is open. It is measured in seconds or in most cases fractions of seconds. The bigger the denominator the faster the speed. For example, 1/1000 is much faster than 1/30. In most cases you'll probably be using shutter speeds of 1/60th of a second or faster. This is because anything slower than this is very difficult to use without getting camera shake. Camera shake is when your camera is moving while the shutter is open and results in a blurry photo. If you're using a slow shutter speed (anything slower than 1/60) you will need to either use a tripod or some type of image stabilization. Some cameras also give you the option for very slow shutter speeds that are not fractions of seconds but are measured in seconds. For example, 1 second, 10 seconds, 30 seconds, etc. These are used in very low light situations, when you're going after special effects, and/or when you're trying to capture a lot of movement in a shot.
When considering what shutter speed to use in an image you should always ask yourself whether anything in your scene is moving and how you'd like to capture that movement. To freeze movement in an image you'll want to choose a faster shutter speed and to let the movement blur you'll want to choose a slower shutter speed. The actual speeds you should choose will vary depending upon the speed of the subject in your shot and how much you want it to be blurred.
Another thing to consider when choosing shutter speed is the focal length of the lens you're using. Longer focal lengths will accentuate the amount of camera shake you have and so you'll need to choose a faster shutter speed (unless you have image stabilization in your lens or camera). The 'rule' of thumb to use with focal length in non image stabilized situations is to choose a shutter speed with a denominator that is larger than the focal length of the lens. For example, if you have a lens that is 50mm 1/60th is probably ok but if you have a 200mm lens you'll probably want to shoot at around 1/250.
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