A few years ago I read about separating my focus button from my shutter release button. It was recommended to me by a fellow sports photographer. I was skeptical at first, but now that have used the back button for focusing I can’t imagine shooting photos any other way. Bellow you will find a short tutorial on using the back button focus for Nikon
What is Back Button Focusing?
Under Nikon’s default settings the shutter release is pressed half way down to initiate auto focus. The shutter release button generally performs three functions. Auto focus, metering, and shutter release. Back button autofocus makes it so the shutter button does not control the focus at all. Instead this functionality is moved to the back of the camera.
How to setup the back button focus button?
Step 1: Go into your custom settings menu
Step 2: Select A (autofocus)
Step 3: Select A5 (AF Activation)
Step 4: Choose AF-ON only
Now your AF-ON button or AF-L, AE-L button is used focus and the shutter release button will only release the shutter.
Why use the back button to focus?
Separating the act of focusing with taking the actual photo has several advantages. You can select your focus point, focus on your subject, then recompose without losing your original focal point.
Another advantage is pre-focusing on a particular point. There are time when I know where I want my focus to be, but my subject is not in that location yet. I will focus on the location then start tracking my subject. When my subject comes into the area that I pre-focused on I hit the shutter release. If my shutter release button was also trying to focus I may get an out of focus shot especially on low light situations.
Also when I shoot sports like football I may focus on a single player. I will often follow the player while he executes the play. There are times when I notice another player will cross in front of the player I am tracking. When I use the back focus button I can release the button when the other player crosses in front of me. I lose focus lock on my original player, but the advantage is reestablishing a focus lock is much quicker. Imaging if the player I am trying to shoot is 40 yards away and the player that crosses in front is 3 yards away. It may take a while to jump from focusing at 40 yards to focusing at 3 yards and then back to 40 yards.
Back button focusing issues
Trying to use the back button focus to recompose your shots work well in many situations, but you need to be mindful of your depth of field. Shooting with a large aperture (small f-stop number) will result in a shallow depth of field. Recomposing may make your shot out of focus.
Moving to using the back button for focusing will take time get used to. It will feel odd at first, but stick with it. In my opinion it is worth it.