Back Button Focusing and Why You Should Use It

Many have heard the term back button focusing but what exactly does it mean and how useful is it? Well today I am going to explain why I think back button focusing is useful in my workflow and why you should consider giving it a try.  

Back button focusing is using one of the buttons on the back of your camera to focus instead of the shutter button. Many use the AF-ON button, but you can customize your camera to focus with whatever button you want.  See image below to see what buttons I am talking about.

The back three buttons on a Canon 5D Mark III

The AF-ON button can be used to activate focus but make sure to disable the shutter button focusing capabilities. Before I show you how to activate the back button focus option, here are some benefits of back button focusing. 

  • Focus, recompose, and shoot without the camera trying to focus once you press the shutter button. This is helpful if you are photographing the same subject in the same plane of focus. An example would be if you were watching waves crashing on a rocky shore. You're already focused, all you have to do is trigger the shutter to capture the decisive moment.
  • Once focused on a subject, don't worry about an object entering the frame once you achieved focus. Since the shutter button will not look to focus, it will just meter the exposure and take the picture. An example would be a group of birds flying in and out of the frame, while your stationary subject bird remains in focus. If using the shutter button to focus, it may try to focus on a different subject.
  • Back Button Focusing and AI SERVO focusing mode work great together. My workflow consists of back button focusing in AI SERVO focusing mode and High-Speed continuous drive mode. I use this setup 98% of the time when in the field. I can still focus on stationary subjects by briefly pressing the AF-ON button, but if something moving enters the scene I will be ready.  An example of this would be using my 70-200mm to make a landscape image near a lake or river. Then out of the blue a bald eagle.. no two bald eagles appear, soaring above, or diving to capture a fish. They start fighting in mid air, tangled in a web of chaos plummeting towards earth. Instead of standing there in awe, having my camera in single shot mode and one shot autofocus, I am ready at a moments notice to capture the epic action. 

This is how to set your Canon 5d Mark III camera to AF-ON focus or back button focusing.

Custom Control for canon 5d III

For the 5D mark III, it's under the menu heading "Custom Controls", as seen in the image above. Once in custom controls you want to set your shutter button half press to metering start and your AF-ON button to metering start/auto focus. Once you made the changes the final custom controls menu should look like the image below.

Canon 5d Mark III


Thats it! It does take some getting used to, but with practice you'll be ready for most any photographic situation.  As far as other camera models, I know Canon has had this option available at least back to the 40D series. Setup was a little different, but it was doable. To find out how to set this option on your specific camera model, please refer to your camera manual.