An Alternative Focus Method: AF-On

I have been focusing my camera a little differently lately thanks to a little used feature on my Nikon DSLR, the AF-On button.  This button that hangs around the back of the camera doesn’t get much love from most photographers but I think if you give it a try you might find that it becomes your primary focus method.

What it does -

When the AF-On feature is activated in the camera, the focusing function is taken away from the shutter relaease button and assigned to this button on the back of the camera. When the button is pressed, the camera’s auto-focus system will activate and focus using whatever AF mode you have selected. It also means that pressing the shutter release button will now only activate the shutter, not the auto-focus.

Why you should use it -

You might have come across a circumstance where you are shooting a subject where there are obstructions that move between you and the subject but you still want to continue shooting with your subject still in focus. If your camera is using the shutter release button to focus you might have trouble maintaining focus because the obstructions are now in front of your focus point. If you use the AF-On feature, you can focus and then release the button and then take your picture with the shutter release button. You can keep taking photos using the shutter release and the camera will not try to re-focus until you press the AF-On button once again. This is also handy if you like find yourself focusing and then recomposing a lot. Usually this means that you have to hold the shutter release down halfway. With the AF-On button, simply place your focus point where you want it, focus the camera, then let go. No you can recompose and not have to press the shutter release button until you are ready to shoot.

It might seem a little weird to use this feature at first but I bet that once you start using it, you won’t want to go back to the old way of shooting.

Comments

  1. John Caradimas says:

    I’ve switched to the AF=ON button at the rear of the camera, when I purchased my D700. And I must admit I loved it.

    When I got my D90 though, I set it up again, in a manner similar to the D700, which however was not as trouble-free. The AE-L/AF-L button, on the D90 is very close to the eyepiece and for a glass-wearing person like me, it means that my thumb (used to press the button in AF-ON condition) is constantly hit by my glasses. Also, the LV button is also under my thumb, so several times I end up activating the LV feature. I wish Nikon would give us a new firmware for the D90, which would allow to totally deactivate the LV function or even better, assign that button to AF-ON.

  2. I tried this shortly after buying my Canon dSLRs, and fell in love. Shooting just seems so much more natural now, and I’ll never, ever give up being able to move my focus away from the shutter release. I was, needless to say, ecstatic when I found out my Olympus PEN E-P1 would let me do the same thing (though not quite as ergonomically).

  3. Since Thom Hogan explained the purpose of the AF-ON button in his Nikon D3 eBook, I use this button as well to focus. As you said, it takes the focus away from the shutter relaease button which is a very interesting feature. I fell in love with the AF-ON button since.

  4. Peter Gamba says:

    While I agree with you, I use this button to lock on exposure, for much the same reason.

  5. Interesting, but I’m not sure it is all that much different than using AF-lock after focusing with the shutter button. Am I missing something?

    • Craig Knap says:

      You, like many, are missing something.

      Using the back focus button ensures you do not have the camera set in the wrong focus mode at the wrong time because pressing the button once locks focus and holding it in switches to continuous focus.

      With the old half-press shutter release to set Single Shot focus, say you have focused on pew that the bride and father will pass en-route to the alter. Now the couple approaches the pre-focused pew, and due to the low light in the church, the camera attempts and likely fails to reacquire the focus when you press the shutter release and the delay causes you to miss the shot. If you hold the shutter release half way down in continuous focus mode focusing on the pew, waiting for the couple to pass by, and someone stands up at the edge of your frame, the camera may shift focus to that person (closest object) and now the camera is focused on the wrong subject when the bride passes by. By using the rear focus button and locking focus on the pew, regardless of low light, or someone entering the edge of your frame, the camera will not attempt to re-focus when you press the shutter release, there is no time lag and you get the shot, in focus.

      Another advantage is for sports and action. Say you are standing along the first base line, and using the back focus button, lock focus on the batter with the back focus button (whose distance will not change until he hits the ball), you can snap away as the batter swings the bat, not having to deal with the lag time of re-focusing. Now the batter hits the ball, press and hold the back focus button and the camera switches to continuous focus and keeps the batter-turned-runner in focus has he runs towards you. No more fumbling with switches on the front of the camera (Nikon) to change from Single Focus to Continuous Focus mode.

      How many times have you handed your camera to someone to photograph you and your group, and because they know nothing about the focusing system they place the focus point on the horizon or building in the background? With the back button focus method you lock the focus on your group from the desired position by pressing the back focus button, hand them the camera (I always try to select someone with an expensive camera, or that I can outrun!) and the focus will not change as they press the shutter release. This is also handy when taking multiple shots of your group when using the self timer or remote on a tripod. You lock the focus once with the back focus button and even if people shift around, the camera will not re-focus between shots.

  6. Paul White says:

    Jeff, thanks for great tip. Because I tend to have the equivalent of the golfers “yipps” when it comes to pressing the shutter release button I frequently resort to using my tripod and a remote cable release. Does the AE/AF lock button on the Nikon D-5000 work with the cable release? BTW, Your Snapshots to Greatshots for the D-5000 has been a wealth of great information.

  7. Rob Yelland says:

    This is a great technique. The Image Doctors’ podcast on Nikonians, May 29, 2008 http://blog.nikonians.org/archives/2008/05/id67_the_image.html has a great discussion on this subject.

  8. Interesting. I will give this a try on my D80.
    Thanks for sharing.

  9. Iskandar Azaman says:

    Great tip…I changed my af button a few years back and have never looked back…

  10. Great tip–I’ve been doing this for years and haven’t looked back. Having the shutter release in charge of focus, metering, and shooting just doesn’t give the photographer much control. Much better to split them and have individual control over each function.

  11. Spodeworld says:

    ” It also means that pressing the shutter release button will now only activate the shutter, not the auto-focus.” Won’t the auto-exposure be activated by the release button too?

  12. loving this tip!

    thank you!

  13. Yes but when you recompose your exposure will change which may be a problem if you are requiring accurate exposure say for a portrate

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