Shutter speed is the amount of time that a digital camera shutter stays open when taking a picture. It works in conjunction with the aperture, which is simply the size of the opening of the lens. Together, the shutter speed and aperture determine how much light is allowed into the digital camera. The light reaches the camera sensor and records the photograph. This combination of shutter speed and aperture determines the exposure of the picture.
When the shutter speed is fast, there is less light entering the camera, and, conversely, when the shutter speed is slower, more light enters. Thus, the photographer can control the amount of light by controlling the shutter speed.
Controlling the exposure is not the only thing shutter speed affects. It also changes the way a photo is recorded with respect to action. Photographers who shoot lots of action, such as sports, rely on very fast shutter speeds to “stop” the action in their shots. As already alluded to, this is much easier to accomplish if there is an abundance of light, since the faster the shutter speed, the more light is necessary to expose the shot correctly.
On the opposite end of the speed spectrum, some photographers specialize in slow shutter speed photography. You can see this in pictures that have silky looking water in a fast flowing river or creek. You can also see it when a night photo is taken of a busy street where all you see are light trails where cars passed. It can be a very creative way to get great looking photographs.
Shutter speeds are set in seconds or fractions of seconds. So, you might see in the picture information that a photo was taken at 1/1600, 1/250, or 1/8 seconds. The higher the denominator (the bottom number of the fraction), the faster the shutter speed. Slower shutter speeds may appear as whole numbers, such as 2 seconds or 5 seconds. When shooting at very slow shutter speeds, it is highly recommended that you use a tripod, because it is quite difficult to hold a camera steady and avoid motion blur.
One other special application of shutter speed is in taking very long exposures. Cameras have a limit to how long the shutter can be held open when taking a picture. In many digital SLR cameras, for instance, the photographer can hold the shutter down for as long as 30 seconds. Other, more typical cameras have shorter “bulb” times available.
A camera can also have a feature that allows the photographer to set a specific time for the shutter to remain open. The time can be measured in minutes instead of seconds. Taking pictures of star trails on very dark nights is done with this feature.
As already mentioned, slow shutter speeds generally call for the use of steadying the camera by using a tripod. There is an accepted guideline for when you should use a tripod when shutter speeds are slow. One might think that he or she can hold the camera steady for a second or more, but this is usually not possible. The general rule is that a person can hold steady for a time equal to the focal length of the lens. For instance, if you are using a focal length of 50mm, you probably can hold the cameras steady for photos taken with a 1/60sec shutter speed. For a focal length of 200mm, the shutter speed should not be slower than 1/200sec.
Many newer model cameras and lenses are equipped with a feature called Image Stabilization. This is technology that has been built into cameras and lenses that compensates for camera shake. Image stabilization is supposed to allow the camera user to be able to hold the camera when slower shutter speeds are being used. Thus, instead of needing a tripod when shutter speed is slower than 1/60sec (using a 50mm lens), it may be possible to hand-hold that camera when the shutter speed is as slow as 1/15sec. Every manufacturer has different claims when is comes to image stabilization, so make sure you check the specifications for the equipment you are thinking about purchasing.
The bottom line when it comes to shutter speed is to know how certain settings will affect the outcome of your photos. Also, when buying a camera, you can check the specs for shutter speeds available on the camera you are interested in. The more advanced the camera you are buying, the more options you will have when it comes to setting the shutter speed.