Marcus Hawkins...

Digital cameras typically have three autofocus (AF) modes: one-shot, continuous and automatic. Different manufacturers use different names for these modes, but they all function in the same way.

As the name suggests, one-shot or single-shot AF is designed for those times you only want the camera to focus once. Half-press the shutter release button to activate the autofocus and once the camera locks on, it stops focusing. It’s the perfect choice when you’re dealing with stationary subjects. Choose continuous or servo AF when you’re photographing moving subjects. Here, the camera will continuously adjust the focus to keep track of the action.

The automatic AF mode switches between the one-shot and continuous modes, depending on whether the camera detects movement or not. It’s good, but not as efficient as selecting the correct option yourself.

Like all automatic options, the camera can get things wrong. For instance, it may focus on something in the foreground or background, rather than the subject. In some situations, the lens will ‘hunt’ for something to lock onto, but if light levels are low, or there aren’t any details that the camera can detect, then it will give up.

Manual focus enables you to correct for these problems. It also allow you to lock the focus at a set distance in the knowledge that the camera won’t refocus the lens – useful if you’re shooting a landscape, for example.

Digital SLRs have a number of AF points that you can see in the viewfinder – anywhere from nine to 65 of them, depending on how advanced your particular camera is. The camera uses these AF points to