Back button focus is one of those photography topics that can quickly garner a plethora of opinions. Many top-level wildlife and sports photographers swear by it. Some have tried it, yet weren’t convinced enough to change. 

Whether you like back button focus, or not, is completely up to you the user. Yet, if this is the first time you’ve heard of back button focus, or you’ve heard of it, but have not yet tried it, you should give it a shot. This article will attempt to tell you why and how.

We’ll discuss in the following what back button focus is, why one would use it, and finish off with instructions that’ll help you to set up your camera if you’d like to give it a try. 

What is Back Button Focus?
Back button focus is the process of taking the autofocus function away from the shutter button and reassigning it to another button on the back of the camera. While you will still fire off shots utilizing the shutter button, you’ll now find focus using the assigned button on the back of your camera (often that button will be the ‘AF-ON’ or ‘AE AF’ lock). 

Why Back Button Focus?
This is a great question because using back button focus is not going to get you sharper images, that’s not really what it is about. So why mess with the way the camera is originally set up if I can get the same images the ‘normal’ way? 

Back button focus is more about having the ability to seamlessly swap focus modes, effortlessly locking focus, and, in theory, achieving a higher percentage of sharper images because you’re limiting the chances for focus errors. Its a simplification of sorts. And it allows you to shoot in single (AF-S) and continuous (AF-C) autofocus at the same time without having to switch in and out depending on your needs. 

For anyone wondering what the heck that last sentence meant, lets break something down really quickly: 

AF-S (‘Still’ or ‘Single’) mode is used when photographing stationary objects that only require you to traditionally half-press the shutter button. Once focus is acquired it stops adjusting it. You can say that focus is locked once it is acquired in AF-S. To get the camera to focus again you need to half-press the shutter once more. 

AF-C (‘Continuous’, ‘AI Servo,’ or ‘C’), meanwhile, controls your focus continuously. When you hold the shutter button down the camera will continually focus on your moving subject. It makes sense to utilize this when shooting moving subjects such as wildlife and sports. 

Those who shoot with back button focus will quickly point out the advantage of being able to leave their cameras on AF-C and still very simply shoot both ways. By pressing the focus button once and letting go if they are looking to lock in on a stationary subject (think a crane standing on a rock) and then work on composing a good image. Then having the ability to instantly and seamlessly continuously focus when the bird leaps to take off and fly away. That’s pretty neat!

How it Works
As long as you have your camera in AF-C mode, any time you need to focus or refocus, you press the focusing button on back. As long as you remain the same distance from your subject, you can let your finger off the button while you reframe or find slightly different compositions. Focus will stay locked on your stationary subject. 

If you need to continuously track your subject, simply hold down the button and your camera will track the moving object. When you are ready to take a picture, engage the shutter release button. Remember that in order for the autofocus to stay engaged, you must hold the back button down while you are tracking a moving subject. It is not a press once to engage, press once again to disengage, system.

Useful Situations
Autofocus can mess up. Wildlife photographers are well aware of the challenges presented when trying to shoot a critter as it moves across brush, or jungle canopy, or wherever. 

If you need to switch quickly between auto and manual focus, back button focus makes it easy. In wildlife photography, it is not a rare occurrence that autofocus ends up achieving a perfectly crisp focus on a leaf just in front of the animal’s eyeball, your intended focus point. Or, it just bounces back and forth picking up whatever might be blocking the animal you are attempting to photograph. With back button focus you can switch to manual focus without having to push any buttons at all, as the autofocus quits when you release the button, so you simply need to twist the lens to adjust focus. That’s not possible when the button to take the photo also triggers the autofocus. And you won’t miss things while fighting with your autofocus as it struggles to decide what exactly it is you’d like the focus to be on. Using back button focus allows you to quickly prevent focus errors like this situation. 

What About Landscape Photography?
Its true that back button focus is likely a bit more advantageous for wildlife and sports photographers than for landscapers. It is not too difficult in that environment to simply utilize manual focus entirely. In landscape photography, finding focus is vital in order to deliver sharpness across the depth of field. With back button focus, simply place your AF point over the area in your scene where you want the plane of focus to fall, and press the focus button once. Now you can compose your image from your tripod, then press the shutter button whenever you like.

Con(s)
Really, the downside with back button focus is that it takes some time getting used to, and while you are learning and forming new habits you’ll likely miss an image or two. Or ten. It’s seemingly a natural part of the process. Don’t believe anyone who tells you that they mastered back button focus right away because likely they haven’t. Frustration will ensue at least once or twice when it takes you more than a few minutes to remember why the “H.E. double hockey sticks” your camera won’t focus as you are pressing the shutter release half-way the way you always used to. Unless this happens to you while on a very expensive African safari where you just missed a Water buffalo strike prey, you’ll probably be able to laugh it off and continue unharmed.  

Once you have established using back button focus, and have a methodical approach to it, the benefits will start to shine through and you’ll likely not go back. Or, you can. The “old reliable” method will always be there for you. 

How to Set Up Back-Button Focus in Your Camera
Setting up your camera requires the ability to tell your shutter button what you want it to do, and usually requires assigning at least one custom feature to a button on the back of your camera. Not all cameras will allow you to do this, so make certain yours will before going too far. For those shooters with Canon, Nikon, and Sony, find (hopefully) easy step-by-step instructions below: 

Canon
Scroll to the Custom Controls screen
In the Custom Controls screen, set the shutter button to “metering start” (which stops the shutter button from engaging focus)
Set the AF-ON button to “metering and AF start”

Nikon
Open the Custom Settings Menu
Select the “Autofocus” tab
Select “AF activation”
Select “AF-ON only”

For Nikon models that don’t have an AF-ON button, you will need to set up the AE-L / AF-L button in the Custom Settings Menu to use it as if it was an AF-ON button:

Open the Custom Settings Menu
Select “Controls” tab
Select “Assign AE-L/AF-L button”
Scroll through the different options in the menu until you find “AF-ON”
When on the “AF-ON” option, select “OK”

Sony
If you use a Sony SLT or a mirrorless camera, you can also move the focusing button to one of the buttons. If you shoot with the latest cameras like the Sony A9, A7 III or A7R III, there is now a dedicated “AF-ON” button on those cameras that you can use for back-button focus.

Click on the Menu button which automatically places you in the first Menu tab (colored in red)
In the first Menu Tab scroll over to screen “AF2” screen
Scroll down to “AF w/shutter” and set that to “Off”