Back-Button Focusing and Why You Should Use It

/ Lars Lentz

back of camera

Back-Button Focus

Ever want to be able to switch from shooting a static landscape to shooting action without having to worry about changing focus modes? Want to capture moving objects in crisp focus? Use back-button focusing and you can have it all. Here’s how to set it up.

Setting Back-Button Focusing

I’ll be showing you how to set it up on my Canon camera, but it can be done on almost any dSLR. What I will do is set my “star” or AE Lock (looks like this -> *  ) button on the back of the camera to be my focus button. Newer cameras have differently named buttons, so choose any available one that is easy to depress with your thumb.

Instead of depressing the shutter button on the top of my camera halfway to both focus and determine (meter) the exposure, I will separate the two. The shutter button will determine the exposure when pushed half way. The back button will focus. Depressing the shutter button all the way will work like normal and take the shot. That doesn’t change. Holding the back button will continually focus on whatever is in front of me, and pressing it only once will focus one-shot style and hold the focus wherever I was focusing while the button was depressed.

Here’s what this will do: I can now focus independently of metering. This means I can re-meter or in other words re-determine the exposure while staying locked on the focus.

A cloud blows over while taking a landscape shot and it is now not a problem. I can stay locked on my focus point and just depress the shutter button half-way to re-meter and determine the new exposure. No more lost shots due to changing light conditions while in the middle of shooting.

A squirrel is running towards me after I have focused on him while he was farther away. No problem. I just keep my finger on the back button focus and the servo takes over and keeps that squirrel in focus no matter how close or far he is away from me.

Here is the method for setting it on my Canon T1i:

  1. Go to custom functions, group IV.
  2. Choose Shutter AE Lock button: AE/AF, no AE lock.

Here is the method for setting it on my Canon 80D:

  1. Set the front shutter button to “metering start.”
  2. Set the back button(s) to “metering+AF start.”
  3. Set the focus mode to “AI Servo.”

Why step 3 on the 80D? Because by having it in AI Servo, when I hold down the back button, it continually focuses, allowing me to follow moving subjects. Very handy and highly recommended for moving wildlife, people, etc. When I take my finger off of the back button, it is just like One Shot mode for landscapes and non-moving subjects. I can just tap it to focus without it continually focusing, allowing me to focus and recompose the scene. It is truly the best of both worlds if set up this way.

aiservo

AI SERVO set to “ON” (circled in red).

Here are a few helpful videos that show how to set back button focus on various cameras:

That is all there is to it. You can always go back if you need to, but I doubt you will ever want to.

Not only will this method help you get more of your shots in focus, but it will also help you keep more shots that would otherwise be ruined by changing real world circumstances.

Thank you for reading what I wrote — I hope you enjoyed it!
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