Back button focus moves autofocus from the shutter button to a button on the back of the camera, so focusing and shooting become two separate actions. This keeps focus locked when you recompose, lets you track moving subjects continuously, and helps you get sharp images more consistently.
Why Separate Focus from the Shutter
By default, a half press of the shutter button focuses and a full press takes the picture. That works well until the camera refocuses at the wrong moment, for example when something passes between you and the subject. With back button focus, the shutter button only takes the picture. Focus changes only when you press the back button.
Set It Up
- Open the camera’s custom function or button menu and find the setting for the AF-ON or similar button. Names differ between makers, so check the manual.
- Assign autofocus to the rear button, and turn off focusing on the half press of the shutter button, if the menu offers that option.
- Check that the button is comfortable for your thumb. Some cameras let you reassign other buttons if the default position is awkward.
- Practice before an important shoot, because the new habit takes a few sessions to feel natural.
Two Ways to Use It
- Single focus (focus and recompose): place the focus point on your subject, press and release the button, then recompose and press the shutter. Because the shutter does not refocus, your focus distance holds.
- Continuous tracking: set the camera to continuous autofocus and hold the back button. The camera follows the subject as long as you hold it. Release it when the subject stops moving, and the focus stays locked.
Step by Step for Moving Subjects
- Choose continuous autofocus and a tracking or zone area mode.
- Pick a shutter speed fast enough to freeze motion. A speed around 1/500 and faster handles many subjects, as a general first guide.
- Hold the back button as the subject approaches and keep the focus area on it.
- Press the shutter when you are ready, keeping your thumb on the button while shooting.
- Release the thumb when you want to freeze the focus distance, for example when the subject pauses.
Common Problems
- Forgetting to press the button, which leaves the lens out of focus. Build the habit of pressing before each shot.
- Handing the camera to someone else, who presses the shutter and finds nothing happens. Tell them about the setup, or switch it back.
- Pressing too hard with the thumb and shifting the camera. Keep a relaxed grip.
FAQ
Is back button focus better for every kind of photography?
It helps most with action, wildlife and recomposed portraits. For fast snapshots, some people prefer the standard half press, so use whichever fits your habits.
Does it work with mirrorless cameras?
Yes. Most modern mirrorless and DSLR cameras allow it, though menu names and options differ.
The Short Version
Assign focus to a rear button, use it to lock or track focus, and use the shutter button only to take the picture. A few practice sessions are enough to make it feel natural.
