Back Button Focus: Why, When & How to Use It
Back button focus transforms a camera’s autofocus system.
Modern digital cameras evolved into elaborate devices over the past generation. Custom settings and automatic functions focus the camera, set the exposure, measure the white balance, and stabilize the image.
Many photographers choose to override some of these automatic functions and take control of the settings. Back button focusing is one such override. It’s a customization that separates focusing from the shutter release button, giving the photographer greater control of the focusing function. And it is beneficial in a variety of situations.
In this post, we’ll define back button focus, why it’s useful in some difficult photography situations, and how to set it up on your camera.
What is Back Button Focus?
Back button focus moves the job of focusing the camera from the shutter release button to another button on the back of the camera. Since these are two functions, assigning them to two distinct buttons makes sense.
Depending on the camera model, it may be a dedicated AF-ON button, as indicated in the photograph below.
Others have an AE-L/AF-L button, which toggles between Auto Exposure Lock and Auto Focus Lock.
With back button focusing, the half-press of the shutter button to achieve focus disappears. The back button focuses the camera. The shutter button releases the shutter.
Taking the Guesswork Out of Focusing
Manufacturers deliver cameras with a combination shutter button/autofocus function. That is a convenient feature; however, it can lead to problems. In some situations, it forces the camera to guess between focusing and releasing the shutter. And that can lead to images that are out of focus.
With the autofocus moved to the back of the camera, we remove the guesswork. With a single button for focus and a single button for shutter release, the photographer takes control of two of the camera’s critical functions.
The camera continues to focus as long as the AF-ON button is pressed. To lock focus, simply release the AF-ON button.
It may seem awkward at first, but learning to use back button focusing can lead to sharper photographs and the ability to react faster in fast-paced situations.
Shutter Button Focus Issues
Relying on the shutter button focus may lead to an inaccurate focus point. In addition, it can cause exposure errors, shutter speed problems, or a delay in high-speed continuous shooting.
For example, after dialing in the settings for a shot, you half press the shutter release button to compose the image. So, the camera refocuses and recalculates the scene’s brightness, even though this has already been done.
Then, the camera takes the photo after guessing at the new settings. So the result may be a soft focus or incorrect exposure.
Back button focusing eliminates that problem because the shutter button does just one job: releasing the shutter. This results in sharp images with proper exposure.
In the photo below, the photographer recomposed the image after locking focus on the baby. Using back button focus, he or she created an area of negative space while keeping the baby in sharp focus.
Tracking Focus at High Speed
As another example, you want a sequence of photos taken of a moving subject at high speed, such as wildlife or a sporting event. The image capture function may be slowed because the camera refocuses and delays the shutter release. Shot missed.
With back button focus, the delay is eliminated. The back button controls the camera’s focus, so the shutter release is activated the instant the shutter button is pressed.
Just reading about this doesn’t seem like such a big deal. But split seconds matter when you are in the field or at the event. It may be a bird or a young soccer player, but the subject moves very quickly.
Take Control of Your Camera with Back Button Focus
With back button focus enabled, focus and the focus point are in the hands of the photographer. For photographers specializing in landscape and outdoor shooting, the focus point is a stationary subject, maybe a rock in the foreground or a faraway mountain. Take control of the lens and camera to focus accurately on the specific part of the scene you desire.
In that situation, I recommend single point or spot focus mode. The photographer chooses the focal point within the composition and locks focus with a press of the back button. Then, adjustments to the composition can be made without losing focus.
Many landscape and nature photographers rely on this focus and recompose method.
An Essential Night Photography Skill
When you’re shooting at night, back button focus takes on an even more important role.
Get enough light on the subject to activate the camera’s focusing function and press the back button. With focus and a sturdy tripod for the camera, you’re all set.
Kevin LJ led a discussion on Focusing at Night and in Low Light that contains some valuable tips.
Don’t Forget to Focus
Disconnecting the focus function from the index finger takes some time to learn. Muscle memory may take over, and you revert back to the shutter halfway focusing technique. And you end up with some out-of-focus images.
Not to worry. With practice, back button focusing becomes second nature.
The Versatility of Back Button Focus
If there is just one great advantage of back button focusing, it’s setting it up with continuous focus mode. For almost all situations, it allows quick and accurate focusing.
This is especially true for moving objects, from athletic runners to wildlife to race cars. Dedicating separate buttons for focus and shutter release allows the camera to function at a higher level.
To capture an image of an animal that is stationary using continuous focus, lock focus on the subject and release the AF-ON button. Focus and recompose.
Then if the animal moves, press and hold the back button focus button. Follow the animal’s movement and press and hold the shutter release button to capture a burst of images.
With back button focus, the camera’s focusing mode changes with a press of the thumb. This frees the photographer to concentrate on composition.
Yet another benefit of back button focus is the ability to employ manual focus without going into the camera’s menu to make the change. This is helpful when something partially obscures the subject. For example, a flower is a subject, but grass or other flower stems capture the camera’s autofocus points, leaving the subject out of focus.
Adjust the focus ring on the lens, don’t press the AF-ON button, and your manual focus won’t be reversed by the camera’s autofocus system. This is a great feature when weather or environmental factors are beyond your control.
How to Set Up Your Camera for Back Button Focus
Each camera manufacturer creates unique menu settings. In this section, I’ll outline some major brands’ basics.
If you’re new to back button focus, it can initially feel clumsy. But I encourage you to try it. If your camera features user settings that you can save, set up a back button focus on one of the saved settings and a shutter button focus on another. Then, if it gets frustrating in the field, you can simply switch back to the shutter button focus.
Nikon DSLR or Mirrorless Cameras
For Nikon cameras with a dedicated AF-On button: In the Custom Settings menu, select Autofocus. Scroll down and select AF Activation, then select AF-On Only. Newer models also give you the option to enable or disable Out-of-Focus Release.
For Nikon models that do not have the AF-On button: In the Custom Settings menu, scroll down to Assign AE-L/AF-L Button and select AF-On.
I recommend continuous focus or AF-C mode in the Autofocus menu in both cases. If you want to set the focus point and then lock focus, simply release the back button.
Mike Hagen gives a detailed explanation for Nikon users in this video:
Canon DSLR or Mirrorless Cameras
These selections vary slightly from model to model, but Canon cameras share some basic menu settings.
Start with the Custom Controls menu or the C.Fn option. Select Shutter Button/Metering and AF Start and toggle it to Metering Start, removing autofocus from the shutter release button.
Return to Custom Controls and designate the AF-On button to Metering + AF Start, activating the Back Button Focus option.
Set the focus mode to AI Servo Mode.
Setting up Canon cameras for back button focus is outlined in this video by Kass Brumley:
Sony Camera Models
At the Custom Settings menu, find AF w/Shutter and toggle it to Off. Then locate the AE-L Button and switch it to AF-On.
Set the camera to continuous focus mode.
Photofonz posted this setup video for Sony:
Set your Fuji camera to manual focus mode.
In the Menu, scroll down to AF/MF. Select Instant AF Setting and toggle this to AF-C.
From the Menu, scroll down to Set Up. Select Button/Dial Setting and change the AE-L/AF-L button setting to AF-L.
The Fuji Guys posted this how-to:
Navigate to the Custom Setup menu. Scroll down to AF/AE Lock and set it to AF-On.
Select Shutter AF and toggle it to Off. Set Autofocus to AF-C.
Here is the Panasonic setup explained by Matti Sulanto:
Customizing Your Camera to Your Specialty
As I mentioned at the beginning of this article, modern digital cameras are sophisticated devices. Knowing your camera’s custom menu and aligning that with what you want to accomplish as a photographer is a game changer. You determine the degree of customization that works best for you.
Settings for exposure, focusing modes, button configuration, and more can be customized to your particular need. Depending on the camera model, custom shooting or user modes allow photographers to set up and save custom profiles.
Then, when conditions change, those profiles can be recalled at a moment’s notice. It can mean the difference between capturing the perfect moment or missing it.
Proper focus is essential to professional photography. An otherwise good photograph is unacceptable without a sharp focus. A thorough understanding of your camera’s focus system will serve you well.
Modern digital cameras make it easy to capture sharp images with out-of-the-box settings. However, we encounter issues when the subjects or settings become more complex.
Back button focus resolves some of those issues. It’s something all photographers should understand. At a minimum, take it out for a test run. Many will find that it gives a boost to your photography.