Nikon’s latest DSLRs come with a “Group-area Autofocus” mode. When compared to the regular Single-Point AF Mode, Group-area AF activates five focus points to track subjects. This focus mode is great for initial focus acquisition and tracking of subjects when compared to a Single-Point or Dynamic AF, especially when dealing with smaller birds that fly erratically and can be really hard to focus on and track. In such situations, the Group-area AF mode might give better results than Dynamic AF, showing better accuracy and consistency from shot to shot.
How does Group-area AF work? Basically, within the viewfinder, you see four focus points, with the fifth one in the middle hidden. You can move all four focus points by pressing the multi-touch controller on the back of the camera (ideally, you want to stay in the middle, because the focus points in the center of the frame are cross-type and the most accurate). When pointed at a subject, all five focus points are activated simultaneously for the initial focus acquisition, with priority given to the closest subject. This differs from the Dynamic 9 AF mode quite a bit, because D9 activates 8 focus points around the center focus point, with priority given to the chosen center focus point. If the camera fails to focus using the center focus point (not enough contrast), it attempts to do it with the other 8 focus points. Basically, the camera will always prioritize the central focus point and only fail-over to the other 8 if focus is not possible. In contrast, Group-area AF uses all 5 focus points simultaneously and will attempt to focus on the nearest subject, without giving preference to any of the 5 focus points.
Group-area AF is especially useful when photographing birds, wildlife and non-team sports. In the above sample image of speed skaters, if your goal is to focus on the front runner, Group-area AF would do wonders, as it would automatically acquire focus on and track the runner that is closest to the camera. Another good example can be a perched bird sitting on a stick and you are looking at it a little from above, so the ground behind the bird is clearly visible. With Dynamic AF mode, whatever you are pointing at is where the camera will initially attempt to acquire focus. If you are right on the bird, the camera will focus on the bird. If you accidentally point to the ground behind the bird, the camera will focus on the background instead. This can get quite challenging when photographing small birds, especially when the branch or stick they are sitting on is constantly moving.
Getting the initial focus point is important and the quicker you do it, the better the chance of capturing and tracking action, especially if the bird decides to suddenly take off. As I have mentioned above, with Group-area AF, there is no preference given to any focus point, so all 5 focus points are active simultaneously. In this particular situation, since the bird is closer than the background, as long as one of the 5 focus points is near the bird, the camera will always focus on the bird and not the background. Once focus is acquired, Group-area AF will also track the subject, but again, only if one of the 5 focus points is near the subject. If the subject moves fast and you cannot effectively pan your camera in the same direction, the focus will be lost, similarly to what happens in Dynamic 9 AF mode. In terms of tracking, I personally found Group-area AF to be pretty fast, but it is hard to say if it is as fast as Dynamic 9 AF – in some situations, Dynamic 9 AF seemed to be a bit faster.
Another important fact I should mention, is that when you use Group-area AF in AF-S mode, the camera will engage face recognition and attempt to focus on the eye of the nearest person, which is neat. For example, if you are photographing someone between tree branches and leaves, the camera will always attempt to focus on the person’s face instead of the nearest leaf. Unfortunately, face recognition is activated only in AF-S mode, so if you photograph fast-moving group sports and you need the camera to lock and track on a subject’s face (and not on the nearest object), your best bet will be to use Dynamic AF instead.
If you would like to learn about camera autofocus modes in detail, I highly recommend checking out the autofocus modes article.