Finding tack-sharp focus is one of the most important components of wildlife photography, if not the most important. Wildlife often moves rapidly and requires photographers to shoot at wide-open apertures with a narrow depth of field. This means that not only can finding focus be challenging, but it can make or break an image. If a photo is not sharp or the background is sharp instead of the animal or bird, then the photo is simply not usable.
Because of those reasons and more, it’s only logical that a lot of emphases are placed on focus and there are many techniques employed by photographers that help ensure consistent and reliable focus, even with fast-moving subjects.
One technique that has proved to be extremely useful for wildlife photographers is ‘back button focus.’ In this article, we will cover what back button focus is, and look at how it can be utilized in wildlife photography. For an in-depth look at autofocus, click here.
What is Back Button Focus?
Back button focus refers to the decoupling of focus from the shutter button. Normally, when the shutter button is depressed halfway, a camera will acquire focus and lock exposure. However, many cameras allow custom button layouts and assignments, thus focus can be assigned to another button on the camera. Most commonly, focus is mapped to a back button, which will be marked as ‘AF-On’ on cameras where the feature is available.
When autofocus is assigned to the ‘AF-ON’ button, depressing the shutter will no longer have any effect or control on focusing. The camera will only focus when the ‘AF-ON’ button is pressed. This seems like a simple change, but it can have great benefits for wildlife photography (and all genres, really).
Combined Focus Modes – Utilize AF-S and AF-C
The biggest benefit of back button focus, in my opinion, is the ability to combine focus modes. With focus mapped to the shutter button, the photographer must select manual focus, continuous focus, or single-shot focus. Reacting to a scene while attempting to change focus mode is almost impossible, and different focus modes are better suited for different situations. Single-shot focus modes are great for a static subject, such as wildlife standing still, manual focus can work well too. Continuous focus modes are essential when wildlife is moving, the focus will track and adjust.
When focus is coupled with the shutter button, only the chose focus mode will work. The huge benefit of back button focus is you can utilize every mode.
For single focus mode or one-shot focus, simply tap the AF-ON button. The camera will achieve focus and then you can release the button, with focus being unchanged. A bonus of this setup is being able to easily recompose while not having to worry about re-acquiring focus. If focus is mapped to the shutter and you recompose, you will have to re-acquire focus, which takes time and can be the difference between getting the shot and not. It is also just much easier to focus and move your camera around for different compositions.
For continuous focus, just hold down the AF-ON button and the camera will maintain tracking and focusing until you release the button. Simple, right? And for manual focus, you can rotate the focus dial on the lens at any time.
Shutter Button Priority is Changed From Focusing to Taking An Exposure
By default, when the shutter button is pressed the camera prioritizes achieving focus before the shutter release kicks in and an exposure is recorded. That ensures focus is acquired but also means there’s a delay in the shutter release. All of us know that every split second matters for wildlife photography, as they can be the difference between capturing a moment or missing it.
When focus is mapped to AF-ON, the shutter button changes its priority to only triggering the shutter release to take an exposure. This benefit mainly shines through when having to recompose. Think about this scenario – you’re photographing a brown bear, the bear isn’t moving, but you move your camera to re-align your composition that puts the bear in a different area of the frame.
With focus mapped to the shutter button, you will have to depress the shutter halfway to initially take an exposure of the bear, then when you recompose, you will have to once again press the shutter halfway to re-focus before taking more exposures. That process takes time.
Using back button focus, you can press AF-ON once to focus and when you release the button, focus is locked and will not change until you engage the button once again. Thus, you can recompose as much as you’d like without having to reacquire focus. If you tried to do that without back button focus, the camera would re-acquire focus every time you recomposed and pressed the shutter halfway down. It doesn’t seem like it makes that much difference on paper, but it saves time and is much more efficient.
Set Up Your Camera
Every camera system has a different set of menu options, but below you can find general instructions for setting up back button focus with various camera manufacturers. If you haven’t tried back button focus before, I highly recommend it. You will benefit from the switch and notice that your focusing in the field is much more efficient. I haven’t gone back since switching to back button focus years ago, it has been a lifesaver in certain situations.
Navigate to the ‘Autofocus’ custom settings menu
Scroll down to “AF Activation” and select it. Choose ‘AF-ON Only’
If your camera does not have a dedicated AF-On button – open the Controls custom settings menu and go to the “Assign AE-L/AF-L Button” option – choose “AF-On”
Change focus mode to ‘AF-C’
Navigate to the “Custom Controls” or the “C.Fn” option in the menu. These options may be slightly different for each camera model
Choose the “Shutter button/Metering and AF Start” option and change it to “Metering Start”, this removes AF from the shutter release
Back in “Custom Controls”, set the AF-ON button to “Metering + AF Start” – this will turn on the Back Button Focus option
Change focus mode to ‘AI Servo’
Navigate to “Custom Settings”.
Locate “AF w/Shutter” and turn this to OFF.
Set the AE-L Button to AF-On.
Change camera to continuous focus mode.
Set the focus selection to Manual
Open your Menu and select AF/MF
Select Instant AF Setting and set this to AF-C
Open the Menu and select Set Up. Choose Button/Dial Setting
Select AE-L/AF-L Button Setting and set this to AF-L/AE-L
Set AF/AE LOCK to AF-C
Open the Custom Setup menu
Select AF/AE Lock and set to AF-On
Select Shutter AF and set to OFF
Note: If your camera does not have an AF-ON button, you can still achieve back button focus. Follow the steps above but treat the AF-L/AE-L as the AF-ON button. You can map focus to the AF-L/AE-L button and use it the same as the AF-ON button. For instance, Fujifilm and Panasonic cameras do not have AF-ON buttons, but back button focus can be used with the AF-L/AE-L and AF/AE buttons.
Matt Meisenheimer is a photographer based in Wisconsin. His artistry revolves around finding unique compositions and exploring locations that few have seen. He strives to capture those brief moments of dramatic light and weather, which make our grand landscapes so special. Matt loves the process of photography – from planning trips and scouting locations, taking the shot in-field, to post-processing the final image.
Matt is an active adventurer and wildlife enthusiast as well. He graduated with a degree in wildlife ecology and worked in Denali National Park and Mount Rainier National Park as a biologist. He also spent 6 months working in the deserts of Namibia before finding his path in photography. Matt’s passion for the wilderness has taken him to many beautiful places around the world.
As a former university teaching assistant, Matt is passionate about instruction. It is his goal to give his students the technical and creative knowledge they need to achieve their own photographic vision. He truly enjoys working with photographers on a personal level and helping them reach their goals.
You can see Matt’s work and portfolio on his webpage at www.meisphotography.com