Back button focus is a technique available with most DSLR camera models but unfortunately rarely used. Many photographers don’t even know they have it. Back button focus disables the double functionality of the shutter release button by eliminating the half-pressing action (i.e., engaging the autofocus system). As a result, the shutter release button will just fire the shutter. Back button focus moves the focusing action to a specific button, usually called AF-ON. When the AF-ON button is pressed, the camera engages the focusing system. When you release the AF-ON button, the camera locks the focus.
Why Using the Back Button Focus Technique
When you first pick up a DSLR camera, your enthusiasm is smitten by the double functionality of the shutter release button. To engage the autofocus system of your brand new camera, you have to half-press the button, keep it like this until the camera ends focusing, and then press it all the way down to take the picture. If you press it too quickly, the camera doesn’t have time to focus, and the image will be blurred. Of course, in time, you learn how to use the double functionality of the shutter button. But in the beginning, it might help you to lock the focus before pressing the shutter button.
Back button focus is also helpful when you photograph an unpredictable subject that can move at any time. Instead of searching through the camera’s menu each time you want to switch between different focus modes (i.e., continuous and single autofocus), you can keep the AF-ON button pressed to focus on your moving subject continuously.
Having control over the focusing action increases your creative freedom and helps you avoid focus mistakes. You can easily lock the focus on the subject and then find the best shooting angle for your composition. You can focus on foreground objects or the background whenever you like. Back button focus allows you to work faster and more efficiently. It is usually a technique preferred by action, nature, and wildlife photographers who need to be fast and adapt to the environment.
How to Set Back Button Focus
Each camera manufacturer likes to have its own menu configuration. To set the back button focus on your camera, you’ll have to read the manual.
First, see if your camera has an AF-ON button. If it does, search the autofocus (AF) settings menu for the option that activates the button as AF-ON. If you don’t have an AF-ON button, you probably have an AE-L/AF-L button. In this case, you’ll have to turn off the half-press function of the shutter button and activate the AE-L/AF-L button to handle the focus. Regardless of its name, the button you are looking for should be on the backside of the camera, near the top right. It is designed to be close to your thumb so that you can easily press it when needed.
You should know all the buttons and settings of your camera. You may not use all of them all the time, but they might get you out of trouble sometimes. Back button focus will need some time to be perfected. Practice when you have time, and see how it works for you. Photography is an exploratory art. A small change in your workflow may be the boost you need to start creating amazing photographs.