What’s this AF-ON button do?

Back Button Focus was a concept I was introduced to while doing a job shadow with Marc J Chalifoux. I didn’t fully grasp the concept at the time (we were shooting a hockey tournament), but I now see how it can be useful.

So what is it? Simply put it moves the focus function from the front shutter button to a button on the back of the camera.
Why would you want to? You can now pre-focus on a subject or area without worrying about loosing focus when you goto press the shutter button.

Perhaps you are at an event, such as a wedding, and you want to capture the bride at the head of the table when she smiles a certain way. If you use the shutter button for focus you will have to press and hold that button down and wait for just the right moment. But what usually happens is you press the button before your ready, or you take your finger off the button and refocus on someone walking by the table, end result is you miss the shot. By switching to back button focus you can pre-focus on the bride and simply press the shutter down when ready. It’s not a feature I can explain in words very well, and to be honest I didn’t understand when it was explained to me. It is simply a feature you will have to try, then decide if it works for you.

Alright- How to set it up.

Apologies to my Nikon friends you will have to pull out your owners manual.
Canon users… well I can show where it is on a couple cameras, it will be similar on other models but you will probably have to do a bit of exploration as well.

Canon 7DII

By default the AF ON button is enabled for focus in tandem with the shutter button.
To change this:
Navigate on the Menu to C.Fn3, choose Custom Controls, and press set

Choose the shutter button and press set

Change to Metering start, and press set.


Your 7DII is now set for Back Button Focus

Canon 6D
By default the AF ON button is enabled for focus in tandem with the shutter button.
To change this:
Navigate on the Menu to C.FnIII and press set

Now scroll to C.FnIII 5 and press set

Choose the shutter button and press set

Change to Metering start, and press set.


Your 6D is now set for Back Button Focus

Steps will be similar for other models, just different locations on menu.
From CANON
Here are examples 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)

I think once you get used to having the back button focus enabled you will wonder why it wasn’t always set.
Set it up and get outside and get some photographs.