Back-button AF: how to master this professional time-saver

    | Photography Tips | 04/10/2013 12:18pm

    Avoid switching between AF modes and ensure sharp images with this clever back button focus technique. In this tutorial we’ll explain why professional photographers often rely on back button AF to guarantee best results.

    Back-button AF: how to master this professional time-saver

    If you watch sports photographers, they’ve often got a thumb hovering over the back of the camera, as well as a finger over the shutter release button.

    This is back-button focusing, a technique that keeps autofocus locked on a moving subject; locks focus on a stationary subject and recomposes; or keeps focus on a subject if something else enters the frame.

    With back-button focusing, you simply press the rear button to lock focus on your subject, take your thumb off and you’ll always keep your original focus point.

    If your subject is moving around a lot, you need to keep the back button pressed down all the time to keep focus-tracking (in continuous or AF Servo focus mode), then press the shutter button when you’re ready.

    How to set up back button AF on your DSLR

    How to set up back button AF on your DSLR: step 1

    01 Find your AF screen
    Every camera model handles back-button focusing slightly differently, but on a higher-end SLR such as the Nikon D600 or Canon 7D, you usually need to assign either the AF ON button (or the AE Lock button) as your main focusing button. We are using a Nikon D800, and we’re going to start by going to Custom Settings Menu>Autofocus.


    How to set up back button AF on your DSLR: step 2

    02 Assign a new button
    On the screen that follows, you need to select AF-ON only from the AF activation screen. Doing this decouples autofocus from your camera’s main shutter release button, but you can obviously still use this button when you want to take the actual shot. If you try and half-press it to focus, nothing at all should happen.


    How to set up back button AF on your DSLR: step 3

    03 Set continuous AF
    Before you start shooting, set AF mode to Continuous (Nikon) or AF Servo (Canon). This allows you to keep focusing on moving subjects by keeping the AF ON button pressed. To lock-focus a stationary subject, press the AF On button to achieve focus, then release it, allowing you to recompose for a better composition.


    How to set up back button AF on your DSLR: step 4

    04 Important caveats
    Now that you’re set up, go and practise! You’ll need to change back to conventional AF activation via the shutter release button if you use a shutter release cable. Also on our Nikon D800, we need to ensure AF-C priority selection is set to Release, again done via Custom Settings Menu>Autofocus.


    How to choose the best AF mode
    How to focus on off-centre subjects
    Creative focus: camera tips for static to spontaneous subjects
    Focus modes: how, when and why you need to change your AF settings
    How to focus your camera for any subject or scene: free photography cheat sheet

    Posted on Friday, October 4th, 2013 at 12:18 pm under Photography Tips.

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