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Okay, some of you may have clicked on this wondering “what on Earth is ‘back button focusing’?” So, first let me explain the concept, then I’ll tell you why I use it, and why you should use it, too.

What is back button focusing?

If you don’t currently use back button focusing (BBF to photographers) you will be holding the shutter release button (the button you use to make the camera take a photo) half way down to initiate autofocus. With back button focusing you remove autofocus functionality from the shutter release button, and move it to one of the buttons on the rear of the camera. It is a bit weird at first, but you soon get used to it, and when you do get used to it, you wonder why on earth you didn’t use it long ago!

The benefits of back button focusing

In my mind there are two very important benefits to using back button focusing, instead of focusing using the shutter release button:

1. When I take long exposure (and night time) shots the camera doesn’t start trying frantically to refocus when I recompose the shot and press the shutter release button. I also don’t need to toggle the AF/MF slider on the lens to MF before taking the shot. When I press the back button and focus on my subject, I just take my finger off it and then recompose. Releasing the back button locks the focus, as long as your subject isn’t moving!
2. One of the problems when taking pictures of moving subjects in AI SERVO mode is that things often come into the frame between you and the subject (other flying birds for example), this confuses the camera, and often it will try to focus on the new moving object in the scene. With back button focus you simply let go of the back button, and the focus will remain locked on to your intended subject until the intruder has left the frame.

These are not major problems, but they are nuisances, and I’d bet you that once you get rid of them by using back button focus, you’ll wish you had done so a long time ago!

Enabling back button focus on Canon EOS cameras

In the camera menu, look for the “Shutter/AE Lock Button” option. Once you’ve found that, have a look for “Metering Start / Meter + AF Start.”

Canon kindly provides a list of the C.Fn menu selection for recent EOS models:

EOS Rebel T3: C.Fn 7 (option 1 or 3)

EOS Rebel T3i: C.Fn 9 (option 1 or 3)

EOS Rebel T4i: C.Fn 6 (option 1 or 3)

EOS 60D: C.Fn IV–1 (option 1, 2, 3, or 4)

EOS 7D: C.Fn IV–1 (Custom Controls — Shutter, AF-ON, AEL buttons)

EOS 6D: C.Fn III–5 (Custom Controls – Shutter, AF-ON, AEL buttons)

EOS 5D Mark II: C.Fn IV–1 (option 2 or 3)

EOS 5D Mark III: C.Fn menu screen 2 (Custom Controls – Shutter, AF-ON, AEL buttons)

EOS–1D X: C.Fn menu screen 5 (Custom Controls – Shutter, AF-ON, AEL buttons)

Enabling back button focus on Nikon cameras

I’m not so sure of my way around the Nikon menu system, but I have managed to find what looks like a great article on the subject of back button focusing with Nikon cameras: How to use Nikon’s AF-ON and back button autofocus.