Getting to grips with… Shutter speeds

This month's installment of Getting to grips with... is all about shutter speeds. Understanding how shutter speeds work and how they interact with the aperture to produce a correctly exposed image is one of the founding principals of photography. Just like the aperture, shutter speeds also have their creative benefits, allowing you to control how motion is recorded in your shot. First though, let's see how shutter speeds can affect exposure...

While the aperture determines the strength of the light reaching your camera's sensor, and controlled by a variable diaphragm that can be open at different apertures to let more or less light through the lens, the shutter speed controls the duration that the sensor is exposed to the light entering through the aperture - long shutter speeds let me more light in, while short ones result in less light hitting the chip. By balancing out the aperture and the shutter speed for the lighting conditions in front of you, you can set the correct exposure for the scene.

For instance, if you wanted to shoot a shallow depth-of-field image on a bright day, you'd set the aperture wide-open at f/2.8, which would let as much light through as possible. With this level of light hitting the sensor, you'd need a fast shutter speed to avoid over-exposing the image. However, if you wanted to shoot a landscape under the same lighting conditions, you'd set your camera at f/16 to ensure detail was obtained throughout the scene. This reduction means there's less light hitting the sensor due to the smaller aperture diaphragm, meaning you'd need a longer shutter speed than you did when shooting at f/2.8 to ensure the scene was exposed correctly. If the prevailing light drops even further - it may become overcast, then you'll need a longer shutter speed still, to make sure your shot isn't under exposed (not enough light hitting the chip).

Just like the aperture, the shutter speed is measured in ‘stops', with each stop doubling or halving the exposure. As an example, changing the shutter speed by a stop from 1/500sec to 1/250sec doubles the exposure time. Most modern DSLRs will also allow you to control the shutter speed in either 1/3 or ½ stops should you wish as well for more precise exposure control. A camera's shutter speed range will vary from model to model, but in the main, 30secs-1/4000sec is the norm, with some top-flight models shooting at up to 1/8000sec, while a compact camera shutter range is not quite as broad. For longer exposures than 30secs, cameras are equipped with a Bulb function - normally the next click after 30secs, with the duration dependent on how long you keep the shutter button depressed for.