Aperture explained

Techniques

24 October 2007 09:37

Together with the camera’s shutter speed, the aperture of your lens controls the amount of light reaching the camera’s sensor. However, it can play a creative role, too. The aperture setting you select can help you control depth-of-field and will have a huge effect on the type of subjects you can shoot.

It’s all too easy to let the camera automatically select the aperture in Program mode or use a safe, mid-range f/8 aperture for every shot. But setting a wider aperture such as f/4 or f/2.8 allows you to shoot in darker conditions because it allows more light to reach the sensor.

Selecting a wide aperture often allows you to use a faster shutter speed combination so you can handhold your camera, without resorting to using a very high ISO setting. In bright conditions a wide aperture allows you to use faster shutter speeds to help freeze fast movement, too.

In contrast, small apertures such as f/11 or f/32 allow you to use longer shutter speeds for creative effects such as waterfall-blur, panning and creating traffic trail shots.

Although apertures relate to the specific lens you’re using, on most DSLRs you can change the aperture using the controls on the camera. Set the camera to aperture-priority mode by selecting either A or Av on the exposure mode dial. This allows you to set the aperture manually, while the camera automatically adjusts the shutter speed according to the brightness of the scene and the ISO speed, thus avoiding under or overexposure.

Using the command dial either on the front or rear of the handgrip, scroll through the available apertures. The display may flash or give a camera shake warning indicating conditions where the camera is unable to set the correct exposure because of extremely bright or dark conditions.