Understanding Shutter Speed

In photography, the shutter is the screen inside your camera that sits in front of the film or digital sensor. ‘Shutter speed’ is how long the shutter on your camera stays open when you press the shutter release.

Shutter speeds are usually expressed in fractions of a second: for example 1/400, which is one four-hundredth of second. Slow shutter speeds become whole seconds (on SLRS, up to around 30 seconds, written as 30”), while fast shutter speeds become very tiny fractions of a second indeed (as tiny as 1/8000 or even higher on some SLRs).

Shutter speed is one of two variables (the other is aperture) that determine how much light hits the film or the sensor inside your camera when you press the shutter release. Darker conditions will usually require a slower shutter speed, a larger aperture, or both, in order to get a good exposure.

If you put your camera into automatic mode (this might be represented by a green square or the word ‘AUTO’ on the dial on top of the camera), then your camera will determine shutter speed by itself. If you put your camera into manual (an M) or shutter-priority mode (an S or a Tv) then you will need to select if for yourself. If you are setting the shutter speed yourself, keep in mind that if your shutter speed is too slow, then your photo will turn out blurry unless you brace the camera; for example by using a tripod. As a rule of thumb, shutter speeds slower than 1 over the focal length you are using (for example, 1/40 at 50mm) will be too slow.

Another consideration is subject motion. If you are taking a photo of a moving subject (for example, a child running, or someone riding a bike), then you’ll need a faster shutter speed that otherwise in order to freeze the motion of the subject (try 1/100 or faster). On the other hand, you may wish to select a slower shutter speed in order to have intentional blur in your composition, as this can give the impression of speed that a frozen subject won’t.