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I’m a big fan of customizing my camera exactly to my needs and back button focusing is one of those things I set up as soon as I get my hands on a camera. Typically, when you want to focus, you press the shutter button halfway down and once you are ready to take the photo, you click it the rest of the way. Now, what is back button focusing? Back button focusing separates the focusing function and the shutter release and assigns them to different buttons. The shutter remains where it has always been on the top of the camera and the focusing function moves to the back of your camera, usually to the AF-ON button, which is operated with the thumb.
Why You Should Make the Switch to Back Button Focusing
Getting sharper images is one of the main goals of every photographer. We buy better lenses, shoot at the right times of day, put our cameras on tripods and use all kinds of tricks, from holding the camera a certain way to making sure we lock the mirror up and bring our remote shutter releases. But a big part of getting sharp images is of course an accurate focus. Back button focusing plays a huge part in getting your focus exactly right as much as possible. It lets you act quicker and removes the need to switch between certain settings, it is great for moving subjects and allows for more stable shots. All in all, there’s much less room for errors and you will experience less missed moments when you decide to make the switch to back button focusing.
Here are the advantages of back button focusing:
No Need to Switch Between Manual Focus and Auto Focus
When focusing with your shutter button, the focus gets reset every time you press it. This is super annoying if you want the focus to stay on one spot and don’t want to refocus for every single shot. Previously, if you wanted to stop the focus from resetting every time you press the shutter, you would have to switch your lens to manual focus. Back button focusing removes the need to do that completely and keeping the shutter and focusing functions on separate buttons is key.
To keep the focus locked in on a certain spot, all you have to do is focus once and you can then take as many photos as you want. Your shutter button becomes just that, the shutter button. The only time I switch my lenses to manual now is when I’m shooting long exposures on a tripod and actually want to zoom in and focus manually.
No More Unnecessary Refocusing
Remember those situations: You are out shooting and every time you want to lock the focus on a subject, you’d have to hold the shutter half way down. It’s kind of absurd when you think about it. You’re stuck in some kind of shutter limbo with your finger just hovering there and getting cramps. If you accidentally let go, your camera will immediately refocus as soon as you touch that button again. With back button focusing, this is a thing of the past.
Especially in situations where neither you nor the subject is moving, this function is worth gold. Just focus once by touching the back button and your focus will remain the same for as long as you decide.
Imagine you are shooting a classical concert. Neither you nor the violin player on the stage is moving and by only focusing once, you will then be able to press the shutter for as many times as you want and you will always get the focus right. With the old method, you’d have to refocus with every single shot and you’d still miss some of it because you might accidentally focus on the background instead.
No More Switching Between One Shot and AI Servo
Two of the main focus modes on a camera that are used the most are One Shot and AI Servo (or AF Single and AF Continuous on Nikon). In the classical shutter button focus setup, one shot means you hold down the button and your camera will focus exactly one time. If your subject moves, you will have to adjust the focus. This is usually used in situations where your subject doesn’t move much, such as portrait shoots. AI Servo on the other hand, tracks the subject and allows for continuous focusing. For example, if you are out shooting wildlife and a lion runs full speed after a zebra, you will be able to keep the focus locked on the lion and shoot as many times as your buffer allows. Assuming you chose a high enough shutter speed, you will still end up with plenty of tack sharp images.
In comes back button focusing, which completely removes the need to switch between the two modes and lets you use AI Servo for all situations. It’s a beautiful thing, especially in situations with an unpredictable subject. The lion might sit still for a few minutes, suddenly start running and plop down again not long after. During all this, you’ll be able to switch between One Shot and AI Servo WITHOUT actually having to change those settings. Set your camera to AI Servo and when the lion is moving, hold down the AF-ON button the whole time while you track the lion and shoot. But you can also use AI Servo just like One Shot. Once the lion sits still, simply press the AF-ON button once and the camera will stop focusing as soon as you let go of the button.
All you have to do is keep in mind that you can’t hold down the AF-ON button when you have a still subject. I have noticed that in this case, the subject will continuously go in and out of focus while the camera keeps trying to track the subject (which isn’t moving after all). Keep this one thing in mind and you will be able to take advantage of both modes without actually having to switch.
How to Set up Back Button Focusing on a Canon Camera
More advanced pro cameras have back button focusing already set up when you take it out of the box – it was the case with my new 7D Mark II – but even if your camera doesn’t initially offer this function, it is easy to set up.
As I have only ever owned Canon cameras and I can tell you how to set back button focusing up on those, but if you are a Nikon, Sony or other camera system owner, you’ll easily find the solution with a bit of googling as well. Even in Canon cameras, every model has a completely different menu setup, but you should be able to figure it out.
First, find the Custom Function or Custom Controls menu in your (usually orange) Canon menu section. The rest varies in every camera, but you should then be able to assign different functions to both the shutter button and the AF-ON button. In my 7D Mark II, the shutter button is assigned to “metering” and the AF-On button is assigned to “metering and AF start”.