Back Button Focus: A Game Changer
Not many people have heard of back button focusing, and of those that have there are many who are not entirely sure of its benefits. For me, using the back button focus is a real game changer in wildlife photography. By the end of this article, I can almost guarantee you will be tempted to make the switch!
For Nikon users, we can shoot in AF-Single (AF-S) or AF-Continuous (AF-C). Those using Canon cameras have the equivalent of One-Shot or AI-Servo modes. AF-S and One-Shot modes mean that your camera focusses at the point you half-press the shutter button. If your subject moves (which is guaranteed to happen at some point with wildlife) you have to release and repress the button to focus again. As a result, most photographers will find themselves looking away from the viewfinder to change between the two modes depending on the type of scene they are shooting. This is precious time, and can often result in missing shots.
Back button focusing allows you to separate the focusing action from the shutter button. So instead you press AF-On when you wish to focus. This allows you to remain in AF-C/AI-Servo mode whilst maintaining the benefits of being able to focus and recompose your shots like in AF-S or One-Shot. Here’s an example:
Whilst photographing this great grey owl perched in the tree, I was using back button focusing. I pointed the chosen focal point (the centre point, as it is most accurate) at the owl and pressed AF-On to focus. Then, having released AF-On, I was able to recompose the shot and press the shutter to take the image. All the time in AF-C mode!
As soon as the owl took flight, I simply held down the AF-On button to track the focus and pressed the shutter simultaneously.
The focus was kept sharp throughout the flight path, rewarding me with a series of usable shots.
Without back button focusing, I would’ve originally been shooting in AF-S so that I could recompose a shot of the owl in the tree. I would’ve then wasted precious seconds switching to AF-C, which can sometimes be fiddly – especially with cold hands in snowy conditions! By then, the owl would’ve probably finished its flight and I would’ve missed the shot.
Further Reading: “How to Photograph Birds in Flight“
There are other reasons why you should make the change, too. You’ll never have to fiddle around with the dials to switch to manual focus. Just don’t press AF-On and it is exactly the same. Perfect the focus with the focus ring, then press the shutter, and your adjustments aren’t altered.
Making the Switch
I imagine that by now you have decided you want to make the switch – at least just to try it out.
For Nikon Users
Go to your menu, and enter the Autofocus custom menu. Scroll down to AF activation (a4) and switch it to AF-On only.
Some older Nikon camera users will find this under the AE-L/AF-L option, in the Controls custom menu (f5).
Note: Make sure that a1 & a2 of the Autofocus custom menu are set to ‘Release’ priority.
For Canon Users
Go to your menu and head to Custom Functions. Select the shutter button, and change its function to Metering Start. Then change the function of AF-On to Metering and AF Start.
If the above isn’t working for you, take a look at this list from the Canon website which will show many users where to find this option:
- 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)
Whilst back button focusing is a very handy tool, it is important that you practise with it first. Don’t forget that your camera will now take photographs when the shutter is pressed without focusing them. Just because you hear that reassuring click no longer means the images are sharp. Enjoy!