What Is Back Button Focus in DSLR Photography?

Take sharper shots with this easy focus method

In photography, focus is the key to stunning images, and with modern DSLR cameras, achieving focus is usually as easy as relying on the auto-focus provided by the camera. But as you get deeper into photography and your subjects become more complicated, knowing how to use back button focus could mean the difference between a photograph and work of art.

What Is Back Button Focus

Back button focus is the practice of using a button on the back of your camera to focus your lens and maintain focus, rather than pressing the shutter button half-way down to allow autofocus to work. In some DSLR cameras, there’s a dedicated back button focus option.

A Canon 60D with a back button focus option called out.

How Back Button Focus Works

Back button focus split the function of the shutter button on a DSLR camera. When enabled, back button focus reassigns the focus mechanism to a button on the back of the camera. When you press the button, the camera focuses on your subject. When you release the button, focus locks on that subject, then, even if you move the camera, as long as the subject remains still, your focal point never changes.

That means the shutter button then only fires the shutter. There's no need to press it halfway down to focus. Just focus using the back button, and then press the shutter button to take the picture. The result will usually be sharper pictures than you could have captured using the shutter button as your focus mechanism.

On some cameras, back button focus has a designed button. It may be labeled as AF On or AE Lock (which is sometimes marked with an asterisk). Other cameras may not have a designated button, but one of the existing buttons on the back of the camera can usually be assigned to work for back button focus.

Why Use Back Button Focus

Most photographers who use autofocus on their DSLR camera use it by pressing the shutter button halfway down. This allows the camera to automatically focus, then the photographer can depress the shutter button completely to capture the photograph. And it works beautifully, in most cases.

However, because that puts the shutter button to work doing double duty—focusing and firing the shutter—there are some instances where this method of using autofocus can be cumbersome and can result in missed shots. Specifically, any instance where you might need to focus a shot and then recompose (such as when you're taking portraits and want to focus once and recompose to shoot several different perspectives) or when you're taking action shots (like shooting sports photography, moving vehicles, or even animals in the wild). Yes, you can keep the shutter button half-way depressed to focus and recompose, but anyone that's ever tried that knows that it's much harder than it sounds.

Instead, most people focus, press the shutter; focus, press the shutter; repeat the process until they've finished taking photographs, or they use continuous shooting, which works, but requires the photographer to press the button halfway to refocus any time the shutter button is released.

It's much easier if there is a button on the back of the camera that allows you to separate the focus and shutter firing mechanisms. This does two things, it eases the ability for you to gain a focus lock to use when you focus and recompose your images, and it also allows you to better focus on moving subject without missing shots during the time it takes to refocus.

In action photography, where the subject is moving, photographers often switch to continuous shooting mode to capture multiple images with a single shutter press. With back button focus, this option is automatically enabled, which allows you to focus on your subject one time an continue to shoot, even as the subject is moving.

The only real drawback to using back button focus is that if you've always used the shutter button to manage your autofocus function, it's going to take some getting used to. Once you do, though, you may wonder why no one ever told you about back button focus before.