How (and Why) to Use Back Button Auto-Focus

Most photographers auto-focus the traditional way: press the shutter down halfway, then compose your shot and pray your subject doesn’t move around. Or press down halfway and quickly take the photo in the same second. This video is demonstrating a different method–one that claims to make auto-focus much easier to manage:

The Three Auto-Focus Settings

Your camera should have three AF modes. (Note that the photographer in this video is working with a Nikon camera; Canons and Sonys use slightly different terminology, but the gists of each are the same.) The three modes are as follows:

  • AF Single Shot. Good for stationary shots, in this mode you press the shutter halfway down and it locks a certain depth of field in focus.
  • AF Continuous. The AF will follow a moving subject after you’ve targeted your subject with the AF icon in your viewfinder.
  • AF Auto. Ideally, this mode switches automatically from single to continuous, but it isn’t always accurate.
An example of why AF Single Shot sometimes doesn't work.

An example of why AF Single Shot doesn’t always work: if your subject moves, you’re screwed.

How Back-Button Auto-Focus Works

Steve Perry of Backcountry Gallery recommends using back-button AF. Again, the term “back-button AF” only applies to certain Nikons, like the Nikon D800, which offers a literal button on the back of the camera that says “AF-On”. (Any camera can designate a back-button to AF, though; the Nikon D5100 has AE/AF Lock; Canons use their asterisk button.)

You have to activate the system first, though, by setting your camera on AF Continuous, then going into the “custom settings” menu, finding “AF Activation” and selecting “AF-On only”.

Now you’ll focus differently: when you want to focus a shot, hold the AF-On button rather than the shutter (which now only takes a photo), and release the button to lock your subject in focus. You can then freely compose your shot and your subject will stay in focus. If it’s moving, you can simply hold the AF-On button down and follow it, the same way AF Continuous works.

canon-slr-back-button

Some Nikon cameras have the AF-on button, making this process much easier.

Advantages of Back Button Focus

Perry lists off three reasons why this AF method is better than the conventional one.

  1. You have more accurate control. Your camera won’t re-focus between shots, the way the shutter necessitates; instead it will keep the same depth of field locked in so you can take multiple shots without worrying about finicky focus.
  2. It’s good for action shots. If your subject is moving, you can follow it by holding the button down to enable AF Continuous mode. Because you’re not switching back and forth between Single Shot and Continuous, you can spend less time dealing with mechanics and more time shooting.
  3. It also works for landscape shots. Because the shutter AF isn’t always accurate, focusing on either the foreground or center, but not necessarily the one you want, and then refocusing every time you release the shutter. This method allows you to lock in what’s in focus, then focus your own attention on composition.

focus-tutorial

Perry ends the video by warning that most people will find this system counter-intuitive, maybe even mess up a few good shots. He recommends sticking with it for a few weeks to realize its advantages, and testing it out on less important shots to get the hang of it. Anyone who’s converted can tell you: they’ll never go back.

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10 responses to “How (and Why) to Use Back Button Auto-Focus”

  1. Thanks for the info. Never knew about it; can't wait to try it. says:

    Always seem to have focus issues, especially when I get excited about a potential shot. Hopefully, this will help the focus issue. Thanks.

  2. Nikon Gal says:

    GREAT TIP!!! Can’t wait to try it.

  3. Don Anthony says:

    Great tip thanks

    Don

  4. david hutchings says:

    brilliant thank you will use this for my motorsport

  5. dan houde says:

    Moved to this technique a few years ago and have never looked back. Only tough when letting someone else shoot with my cams.

  6. David Corito says:

    Great tip I now know how to really use the AF/L button on the back of my camera. I never used it the way you described in your video. Can’t wait to try it.

  7. Rick Montes says:

    Outstanding

  8. Crunk says:

    When I use big aperture, does the photo blur if I use the back-button lock the AF and then composition the picture???

  9. Jane MNT says:

    Great job of teaching AF, AU …., but ….I prefer you spoke slowly . Thanks

  10. karen coffee says:

    I’d heard about back button auto focus but didn’t understand it. Thanks for your clear explanation. Ill try it for a couple of weeks.

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