I recently posted this thread on the Nikon digital Learning Site and as I was going over the comments I thought it would make a great Tech Tuesday so, here it is…
Do you choose AF-S (single focus) or AF-C when you point your camera at your subject? If you are shooting stationary subjects, you likely have the focus set to AF-S which means, you select a focus point, depress half way down on the shutter button, the lens focuses on the target within the selected focus point, and as long as you keep the shutter button halfway depressed, the focus is locked. You can move the camera to different compositions and the focus will stay on the distance setting that you locked in…until you lift your finger off the shutter release.
That’s great for stationary subjects. What about moving targets? There’s AF-C (continuous focus) where point the camera at your subject, depress the shutter release halfway down and the lens focuses on your subject. When the subject begins to move the camera kicks in to continuous focus and follows the subject, changing focus as needed while we fire off a sequence of shots.
Pretty straight forward…but, what happens when you are in single focus and your subject begins to move? You have to either quickly change the focus to continuous (oh, yeah, the subject is long gone by now) or you reach up and take control of the focus using the manual focus ring on the lens (a very viable option… if you have an AF-S lens), or you keep the camera in continuous and when the subject falls out of the focus point range you simply switch to single focus (and forget to switch it back for the anticipated action) or, once again reach up and take control of the focus manually (again, if you have an AF-S lens).
I shoot action a great deal of the time so, I want to be set for action…continuous advance and continuous focus. But, there are times when the subject falls out of the focus area (even with 51 focus points this can happen) or I need to lock focus for several frames. Invariably, I would switch to single focus and forget to switch back (ok, maybe most of you don’t have this memory issue but for those of you who do…) to continuous and miss a great sequence.
Enter the AF-ON button on the rear of many cameras. (AE-L/AF-L works if you don’t have AF-ON on your camera. Check your manual for specifics on these settings for your camera). These settings are based on the D3 family. Now, I leave my camera set to AF-C and I have programmed my AF-ON button to be focus and exposure lock (AE/AF lock. Custom setting a9 on D3 series bodies). Now I have the best of both worlds. I have the ability to track moving subjects and when I need to override the continuous, I simply focus on my subject and depress the AF-ON button (and hold it) recompose and fire away. To get back to continuous focus, I simply release the AF-ON button. and begin tracking my subject.
The reason I have set the AF-ON button to be both focus and exposure lock is that the focus point plays a part in the overall exposure of an image. When I point the camera at a scene and focus, some of the exposure is determined by the focus point selected telling the camera that this is the subject which in turn affects the exposure. So, I lock the exposure at the same time I lock focus and shoot away.
*The AE-L/AF-L button (Custom f6 has several options to program in to this button but, one of the primary settings is exposure and focus lock.
Here’s an example of how I use the AF-ON to bounce between focus lock and continuous focus…
Shot from a bouncing boat, I locked focus on the bird, held the AF-ON button and fired off a few shots.
My camera reverted to continuous focus (Dynamic 21 point as discussed in a previous post) when I released the AF-ON button to allow me to track the Kittiwakes flying overhead.
As the boat drifted closer to the Kittiwake nests, I aimed at the birds, focused, held the AF-ON button to lock focus (remember, I’m on a bouncing boat and the focus kept changing from the bird to the rock, rock to the bird as we bounced up and down) and fired off a burst. I was then able to select the shot with the birds composed the way I wanted without any concerns over which image was in focus.
Whenever a bird would come in to land on the rock, there would usually be some interaction amongst the birds. Continuous Dynamic allowed me to capture this exchange
Take time to think about how you shoot… do you have your AF-ON, AE-L/AF-L buttons programmed to suit your style of shooting?
