AF-On And Back Button Autofocus
Try a better way to focus your DSLR! Using back button autofocus is a faster, easier, smarter way to get great AF results from your DSLR. This video will show you how AF modes work – and why decoupling autofocus from your shutter release can take your photography to a whole new level.
This method works both for camera with a dedicated AF-ON button or by reassigning a button on the back of your camera for autofocus.
Follow Up Notes and FAQ
This turned out to be a really popular topic and I’ve had quite a few questions come in regarding this technique. So, I’ve put together some notes and a few commonly asked questions that should make the transition from shutter release AF to back button AF much easier.
When I try this technique on my Nikon, I focus and recompose, but my camera won’t fire. The only way I can get the camera to take a picture is if the AF point is right over the spot that I focused on.
This behavior occurs when the camera is set to “Focus Priority” for AF-C under the custom functions menu. By default, most cameras will use what’s called “Release Priority” when they are switched to AF-C mode, so most users will not run into this issue.
However, sometimes a camera is set to “Focus Priority”, meaning the camera will ONLY fire if it has a 100% focus lock under the current AF point. This behavior is fine when you’re locking in focus with the shutter release or you happen to have the AF point right smack dab on the area where you want to focus. However, with Back Button AF it causes an issue since you can no longer focus, recompose, and shoot (the AF point may no longer be over an area that’s in sharp focus).
So, make sure your AF-C focus Priority is set to “Release” under your custom menu. Usually it’s the first option for most Nikon cameras.
With shutter button AF, my VR was activated when I pressed partway down on the shutter release to focus. When I use the back button, VR no longer activates when I focus. How do I handle this?
The answer to this is going to depend on your camera. If you have a newer Nikon body (like a D800 / D4 etc), using the back AF-On button will actually activate VR. For older cameras, it’s only activated with a half press of the shutter release.
However, don’t let that stop you!
I used this method a long time before it was linked with the shutter AF-On button on the back of the camera. In fact, I prefer VR to be available with a half press (it still is with newer cameras, it’s just been added to the AF-On button).
The reason I prefer it with a half press of the shutter release is that I can keep VR active before the action starts. This is critical since VR needs a few seconds to stabilize before you start shooting. If you simply focus and shoot at the same instant – before VF has had a chance to stabilize – you’ve lost all the benefit of using it. So, use your back button to AF, and hold halfway down on the shutter release until and wait for that perfect moment. Then, just a little extra presser from your finger snaps the shot.
What about using dynamic AF? Like d9, d21, or 3d tracking?
No worries – it works exactly the same as if you were using your shutter release for AF. The next question is why / how to use those dynamic AF tracking modes, but that’ll be another video. (hint – most people should probably start with 21pt)
My camera used to beep for focus confirmation, now it’s not doing it – what happened?
Unfortunately, this is one downside of this method, you’ll no longer get that focus confirmation beep. However, I’ve learned to keep an eye on the AF confirmation dot in the viewfinder and have never really missed the beep. Besides, for the most part you can see if the subject is in focus or not right in the viewfinder. Old school style
Do you always focus with just the center AF point and recompose?
Nope, I did it that way for the video to keep things nice and simple, but most of the time my recommendation is to select the AF point that the closest to the spot you’d like to focus on. Sometimes you get lucky and you’re able to put the AF point right over the area you want to focus on, other times you’ll need to recompose, but at least it’s a minimal amount. Either way, this method has worked great for me.
Are there any limitations when using flash units?
Under normal circumstances, no, this works just like shutter release AF. However, this is one exception to the rule and that’s if you use the AF Assist Illumination feature – this method doesn’t support it (at least with Nikon).
Why do all these questions seem to involve Nikon cameras? What about Canon?
Unfortunately, I don’t own any Canon cameras at this time, so I can only speak to what I know about the Nikons and encourage Canon users to apply the concepts to their cameras. I do plan on getting a Canon body down the road for instructional purposes.
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This tip is filed under: Gear Talk