HIT THE BACK BUTTON

Mike Harris has all you need to know about back-button focusing: what it is, how to set it up and why you should be using it

- Mike Harris

10 MINS We often mention back button focusing in passing. However, if you’re relatively new to photography, or just haven’t got round to trying the technique yet, you may not be familiar with it, so here’s a fuller introduction.

You might think there’s very little to explain – you simply use a button on the back of the camera to focus. However, for back-button focus to work effectively, you need to remove the shutter button’s ability to engage autofocus when half-pressed and you need to switch to continuous-servo AF. There are several reasons why back-button focus is advantageous, and they apply to a variety of shooting situations.

You no longer have to spend time switching your camera’s continuous/ AI Servo and single area AF modes, because when you lock focus (by releasing the back button) you can fire the shutter without the camera hunting or refocusing. This also means that you don’t have to use AF lock, or switch to manual focus to lock the focus. This is particularly helpful when photographing sports or wildlife. A good example would be capturing a subject in tall grass. A slight breeze could cause blades to obscure your subject and confuse the camera’s AF system, making it hunt. With back-button focus you could simply lock onto your subject without switching from continuous AF and fire the shutter at will.