Choose the right AF mode
Accurate focusing is, of course, vital for sharp photos. The majority of cameras across the Nikon range offer the same three autofocus options – single-servo AF, continuous-servo AF and auto-servo AF. Choose single-servo when the subject is stationary, as once the camera achieves focus it stays locked at that distance.
If the subject moves closer or farther away after focus is locked then they’ll be blurred in the photo. If you want to track a moving object, then continuous-servo is the AF mode of choice. Here, the camera never locks the focus, constantly adjusting the focus distance in response to movement detected by the active AF points. The downside is that if your subject becomes obscured then the camera will potentially refocus elsewhere. Higher-end Nikon cameras let you fine-tune the sensitivity and speed of continuous servo to avoid this.
Auto-servo AF might sound like the perfect compromise when you’re trying to work quickly. It initially locks onto the subject covered by the focus point but will then automatically switch to continuousservo AF to track the subject when the focus point discerns a change in distance. The drawback is that you’re relying on the camera to make a judgement call on whether the subject is moving or not, and having to wait that split-second longer to trigger focus tracking might make the difference to getting the shot or not.
Despite the Usain Bolt-style acceleration built into the likes of the D500 and D5, you can’t expect the camera to reach top autofocus speed from a standing start. If the subject is small in the frame or lacks contrast for the AF sensors to ‘bite’ onto, then there’s also a risk that the camera will focus the lens back and forth, hunting for the subject. But you can give your camera a fighting chance by pre-focusing at roughly the distance at which you anticipate the action will take place. In some situations, it may even be better to pre-focus on an area and switch the lens to manual focus to lock the setting in, as Andy advises below…