Back button focus is a camera technique that separates the autofocus function from the shutter release button, allowing you to focus and take the shot independently.
How Back Button Focus Works
With back button focus enabled, the shutter release button’s sole function is to fire the shutter, while focusing is controlled by a dedicated button (often labelled “AF-ON”) on the back of the camera body.
You use your thumb to press this rear button to acquire and maintain focus, while your index finger remains on the shutter button to capture the image.
What Does BBF Do?
This separation of focus and shutter release provides several benefits. You can lock focus on a subject, recompose the frame, and shoot without having to re-acquire focus.
- It allows seamless switching between single-shot autofocus (focus and lock) and continuous autofocus (constantly refocusing on a moving subject) simply by holding or releasing the back button.
- It eliminates shutter delay caused by the camera’s focus priority settings.
- It provides more control and flexibility, especially for action/sports photography.
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When to Use Back Button Focus
Back button focus is particularly useful in situations where:
- Your subject is moving erratically, requiring constant refocusing.
- You need to quickly lock focus and recompose the shot.
- You’re photographing fast action and want to eliminate focus delay.
- You frequently switch between static and moving subjects.
It’s a popular technique among wildlife, sports, and action photographers who need precise focus control.
Which Cameras Have BBF?
Most modern DSLRs and mirrorless cameras from major brands like Canon, Nikon, Sony, Fuji, and Panasonic have a dedicated AF-ON button or allow you to assign back button focus to a customisable button.
Benefits of Back Button Focus for Portraits
Using back button focus for portrait photography offers several benefits:
Easily Switch Between Focus Modes
With back button focus, you can seamlessly switch between single-shot autofocus for static portraits and continuous autofocus for portraits with subtle movements, simply by holding or releasing the dedicated focus button. This flexibility allows you to quickly adapt to your subject’s pose and movements.
Maintain Focus Lock While Recomposing
When using single-shot autofocus, you can lock focus on your subject’s eye, then recompose the framing without having to refocus, ensuring tack-sharp portraits.This is especially useful for off-centre compositions or when working with a shallow depth of field.
Avoid Accidental Refocusing
Since the shutter release is decoupled from the focusing mechanism, you won’t accidentally refocus when taking the shot, even if something crosses in front of the camera.This prevents unintentional focus shifts that can ruin a portrait.
Precise Focus Control
With your thumb on the dedicated focus button, you have precise control over when and how long the camera acquires focus. This level of control is invaluable for portraits, allowing you to confidently focus on the most important part of your subject.
Reduce Shutter Lag
By separating focus and shutter release, back button focus can help reduce shutter lag, ensuring you capture fleeting expressions and poses. While back button focus requires some practice to master, many portrait photographers find the added control and flexibility to be invaluable for consistently nailing focus on their subjects.
Using BBF for Video Recording
The reason back button focus is typically disabled for video is that continuous autofocus is required when recording moving subjects. Back button focus is designed for locking focus at a set point, which is useful for still photography but not ideal for video.
When recording video, the camera’s default autofocus modes (continuous AF or AF-C) are better suited, as they will continuously adjust focus as your subject moves around the frame.
These AF modes are usually controlled by partially pressing the shutter button or using the camera’s autofocus lock button during recording.
So in summary, while back button focus is an extremely useful technique for still photography, allowing you to lock focus and recompose shots, it typically cannot be used effectively for video recording on most camera systems.
The continuous refocusing needs of video make the standard autofocus modes more practical for that use case.
