A few weeks from now, we will be in Florida and I plan to do a lot of bird photography again. My Nikon D7200 has several autofocus options, including 1 AF point, 9 AF points and 51 AF points. Which of these do you recommend for birds in flight—when I am using Continuous Autofocus—to maximize my odds of getting more sharply focused photos?
This is an important consideration regardless of the brand of camera, Kellie, since most offer several options as to the number of active focus-detection points. The concept is similar regardless of the exact number of points or the terminology used by the manufacturer. In a nutshell, here’s how each option works and when/why you might want to use it. In some respects, this also applies to sports photography, especially when the subject is far from the camera and small in the frame.
Single-Point AF: This is ideal for static photos since it allows you to specify exactly where the camera should focus, for example, on the nearest eye in a close-up portrait. However, when a bird is flying around erratically, it’s often impossible to keep focus on the most important part of its body (the head). And when a small bird gets completely off-centre in the frame, the single-point AF system will definitely lose focus. It’s highly unlikely that it will later re-acquire focus if the bird moves back into the area covered by the small focus-detection point.
Multi-Point AF with numerous detection points: When you set the AF option that will activate all of the available focus-detection points, the camera should be able to set and maintain focus on a subject just about anywhere in the frame. This is ideal when a small bird might be in the centre of the frame at one instant, in the lower left part of the frame in the next instant, and in the upper right part of the frame in the next. As the bird’s position in the frame changes, at least one of the numerous focus-detection points should be able to find it. The system will then change to using some of the other points as necessary. The drawback with this option is that the camera must process data provided by numerous points, and this will probably slow the process somewhat.
Multi-Point AF with fewer points: This mode (activating 9 or 11 points, depending on the camera) should provide faster, more reliable AF with an erratically moving bird since the camera needs to process less data from the fewer points. Most of the expert bird photographers I have worked with recommend this option. It’s not quite as versatile as Multi-Point AF with numerous focus-detection points; in other words, it’s more likely to lose focus on a small bird when it moves far off-centre. Even so, after six raptors in flight bird photography workshops, it’s the one that I use 90% of the time. Granted, I will switch to the maximum number of focus-detection points when I am certain that the bird will never get close to the camera. In such a situation, the subject will always be small in the frame, making the other AF option preferable for the most in-focus photos in a long series.