Let’s review…light is everything in
photography. It enters the camera
via the aperture, and the shutter
speed.
The shutter is that thing in your camera that 'clicks' when you take a picture.
The shutter speed refers to the length of time the shutter stays open wen you're taking a photo: the longer the shutter stays open the more light enters the camera, the shorter amount of time the shutter stays open the less light enters the camera. Remember, how much light enters the camera determines the appearance of your image.
Shutter speed is measured in seconds or fractions of a second. A shutter speed of "1" (one second) is considered a slow shutter speed; a shutter speed of "1/1000" (one-thousandth of a second) is considered a fast shutter speed. While the aperture is used to control the depth of field (how much of the photo is in focus), shutter speed is used to convey the motion of the subject in your photo.
If a person or animal were to dash across your line of sight and your shutter speed was set to "1" it would result in a blurred image as a lot of movement would happen during the slow setting of one second.
If the shutter speed was set to "1/1000" it would capture the subject as if frozen in action.
Capturing Motion = Purpose of Shutter Speed
So to recap:
- Aperture controls depth of field
- Shutter speed controls the motion