For the purpose of focusing a D-SLR camera, pressing the AF-ON button has the same effect as pressing the shutter-release button halfway. To set the camera to use the AF-ON button for focusing, you will need to set a custom function, which can be found in custom settings, under Autofocus. This technique is also called back button focus.

The default setting on Nikon D-SLR cameras sets Shutter/AF-ON in which both the shutter-release button and the AF-ON button can be used to initiate autofocus; or you can choose to set the AF-ON button only for focus, which means only the shutter-release button will only activate the shutter (snap the picture) when pressed.

We spoke with three professional photographers—who specialize in different types of photography: sports, wedding and wildlife—to find out why they use the AF-ON button for focusing.

Commercial sports and action photographer Jay Watson explains that once he got used to using AF-ON only for focusing he found it to be advantageous for shooting both moving and static subjects. “I keep the camera’s AF set to AF-ON only, and start that way for most assignments. Overall it’s a set up for fast performance. However the camera now feels more personalized, and the AF settings are more intuitive which is important not just for sports. If you’re fussing with camera settings in front of a subject, you’re less engaged and more likely to miss an opportunity,” he says.

Wedding and portrait photographer Gary Small says he sets up his cameras to “disconnect” the focusing from the shutter release button because he can’t miss the first time around when it comes to photographing wedding and other events. “The shutter won't fire if the camera doesn't lock focus, there's a huge risk that an important shot will be missed. Try explaining to the bride and groom and their parents why you missed the kiss at the end of the ceremony, or of their grand entrance, that once in a lifetime shot, because the camera wouldn't lock focus and fire when you needed it to. The way I do it, I lock focus in advance and the camera will fire every time I press the shutter release. This means I get my shots every time.”

“What happens if you’re all set and know the camera will focus fine, but then at the moment you go to take the picture, someone walks in front of you or in the foreground and causes the camera to refocus on them, and your subject (let's say the bride up in a chair during the Hora at a Jewish wedding reception) is suddenly out of focus and you blew the shot? Again, once I press the AF-ON button, I can shoot to my heart's content, and as long as the distance doesn't change, I will get a whole series of images and action shots and not miss a thing. As far as I'm concerned, those two reasons alone are compelling enough.”

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Benefits of Using the AF-ON Button for Autofocus

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