Quick Guide to Understanding Shutter Speed

source : click here

Written by Ron Risman

In a film camera, light travels through the lens opening (aperture) and past a shutter that opens and closes to allow light through to the film. While a digital camera doesn't have a mechanical shutter, it does use electronics to simulate this same process.

As light travels through the lens opening (aperture), the shutter opens and closes in a timed fashion to determine how long the image sensor ("film") gets exposed to a scene. A faster shutter speed, similar to blinking your eye more quickly, helps to reduce the amount of motion the cameras image sensor will capture. If the shutter stays open longer, it will allow more potential motion in the captured frame. Any movement during the "capture" process of a scene will end up as a blur. If it's camera movement then the entire photo will be blurred. If only the subject moves then only the subject will be blurred.

In order to capture blur-free "action" photographs (Sports is one example), you'll need to make sure the camera is using a high shutter speed. Typically a shutter speed setting of 1/125th of a second (shutter speeds are measured in fractions) is considered a "high" shutter speed, although the setting will depend on the speed of the action that you want to "freeze". Example: To capture a golf swing you might need to use a 1/500th speed shutter, while trying to capture kids playing basketball might only require a 1/125 or 1/250 shutter speed.

Important: Less light gets through to the imager (or film) as the shutter speed is increased, thus it's very difficult to use higher shutter speeds in lower light situations. There are ways to improve the speed of the shutter in these situations. One is to allow more light to pass through the lens (aperture setting), the other is to increase the ISO sensitivity of the imager.