The back-button focusing mechanism on cameras is a very useful tool for separating the twin functions of focusing and shutter release.
Usually, when you press the shutter release button, the camera would first lock focus and then release the shutter mechanism to capture an exposure.
When you use the back-button focusing system, this focus lock step is no longer triggered by pressing the shutter release button. Instead, you have to assign a button at the back of the camera that will activate the autofocus mechanism when you press it.
The shutter release button will continue to be the trigger for releasing the shutter mechanism. However, with the autofocus functionality now triggered by a button at the back of the camera, the shutter release button will respond quickly.
Key Takeaways:
Benefits of Using the Back-Button Focusing Mechanism
As you can understand from the previous segment, the whole purpose of using the back-button focusing system is to save precious milliseconds when you are out in the field shooting photos. If both the functions of focus lock and shutter release are taken care of by the shutter release button, you lose critical milliseconds when your camera is focusing. By splitting the two functions, the shutter release button releases the shutter mechanism instantaneously.
Many of you will probably argue at this juncture that one could easily use the release priority mode (Nikon systems) rather than the focus priority mode to overcome this problem.
I would beg to differ.
If you switch to the release priority mode, the camera will no longer confirm a focus lock before releasing the shutter mechanism. It is not the ideal way to handle a situation where your subject may be moving around within the frame.
The release priority mode works when there is a fixed distance between the subject and the camera, and therefore it is not required to readjust focus from shot to shot.
For example, if you are shooting wildlife photography, your subject is not going to be stationary for long.
The problem is magnified when you are using a wider aperture. With a wider aperture, your depth of field is smaller, and therefore there are higher chances of your subject going out of focus if the distance between the subject and the camera changes.
If you are using a comparatively smaller aperture, you have a bit more room to play with in terms of depth of field.
Using the back-button focusing is a much better solution in a situation like that. You can easily keep the subject in focus as it moves around in the frame.
Another critical advantage of this method is that it allows me to switch between single and continuous autofocusing without having to change settings back and forth.
Many times, when I’m shooting a relatively stationary subject, I use single-shot autofocusing. It helps me to lock focus and then release the shutter in a traditional way. The problem happens when the subject starts moving.
For example, when you are shooting fashion photos, environmental portraits, or any other genre where the subject is not absolutely still, you cannot use the single-shot autofocusing mode.
Continuous autofocusing helps to keep the subject’s eye in focus at all times. The problem is once you set your camera to single-shot autofocusing, to move back into continuous auto-focusing you have to change settings again.
With back-button focusing, all you have to do is set your camera to continuous focusing. When you need single-shot autofocusing, press the back button once to lock focus and then release it immediately after.
In order to use the camera in continuous auto-focusing mode, press and hold the shutter release button to keep the focusing motor engaged. This can be a really big help when you are shooting some genres.
Back-button focusing is also critically beneficial when shooting subjects that are very small. For example, when you are shooting photos of bugs, flowers, and small products, sometimes the camera does not focus where you intend it to. In such situations, you can switch between autofocusing and manual focusing and even use the focus and recompose technique, all with a single setting.
Use Case Scenarios for Back-Button Focusing
The two primary use-case scenarios of the back-button focusing mechanism are sports and wildlife photography. I have tested the back-button focusing on both genres. My experience in wildlife photography, particularly in bird photography, has been a pleasant surprise.
Although this is not a new technique, and I’ve been using this for well over a decade, the first time I ever used this technique helped me save precious moments and get a lot more keepers than I usually do otherwise.
The header image I shot with an archaic D7000 some years ago on a birding trip, I was on a boat that was moving parallelly to the bird. Also, the bird was moving its head from side to side. This is where the back-button focusing technique helped me nail the shot.
One thing that was not in my control was the position of the Sun. It was too high and I was shooting up. So, the catchlight was not ideal.
How to Set Back-Button Focusing on Your Camera
Every camera make has a different way of setting the back-button focusing mechanism. Let me explain a couple of options from Nikon systems.
Let’s first look at the D5500, which is an entry-level APS-C DSLR from Nikon.
You have to get into the menu first. From there go to the Custom Setting Menu. Under that, you’ll find the Controls option. Under that, there is the Assign A-EL/A-FL button option. Choose AF-On.
Your camera is now set for back-button focusing.
On cameras like the full frame D850, get into the Menu option. Go to the Custom Setting Menu. Go over to Autofocus. Then select AF activation. Underneath AF activation you will find two options – Shutter/AF-ON and AF-ON Only. Choose AF-ON only.
Verify in the Custom Control assignment option under Controls to confirm that the AF-On button has been assigned to the AF-On functionality.
This means autofocus will now trigger only when you press the AF-ON button at the back of the camera.
On Canon systems, you’ve to press the Q button and get into the Customized controls option. Select Customized buttons. Underneath change the setting on the Shutter button from Metering and AF start to just Metering start.
Now, go to the AF-On button and change it to Metering and AF start. These two changes take away the autofocusing functionality from the shutter release button and assign it to the AF-On button.
Assigning a Second (Backup) AF Control Button
Depending on the genre of photography that you do, you may need to change the autofocusing area from time to time. For example, for a majority of shooting situations, I would use a single point of focus. This helps me to pinpoint my focus point on a subject’s eye.
However, when I am in a situation where the subject is moving around, I find it necessary to change my focus point selector to group area mode because it gives me better control over focusing accuracy in a dynamic environment.
This happens quite a lot when I’m photographing birds.
In a situation like this, I need to have a backup button that allows me to switch from single point AF to group area AF without having to dig into the settings. I have assigned the multi-selector button at the back of my D850 for this.
In case you do not have a professional camera, it may be difficult for you to choose a button that would serve as the second focusing button for you.
Conclusion
Back-button focusing is a highly valuable tool for all types of photography. It doesn’t matter what level of photographer you are or the type of photography you practice; you’ll discover that it saves you time and offers added convenience during your shoots. I strongly recommend giving this technique a try, and I’m confident it will immediately enhance your photography experience.
Leave a Reply