All Photos by Eric Bowles
By Eric Bowles
With all the talk about new cameras, we get the impression that focus is suddenly like magic – a new secret sauce that will make all your photos perfectly sharp. Sadly, that’s not exactly the case. Yes, there are new technologies that help with focus, but photographers still must do their part. Let’s take a closer look at what you can do to create more images that are sharp and in focus.
There are, of course, lots of different cameras. And depending upon when a camera was developed and the intended market for that camera, performances will vary. In general, newer cameras bring better focus performance with a range of scene- and subject-recognition technologies. These new focus technologies mean the learning curve with a new camera may be steeper, and your old settings and techniques may not apply. Part of focusing is knowing what settings to use and how to help your camera focus quickly and accurately.
No matter the camera, there is a limit on how much data can be processed quickly. So the general guideline would be to use the smallest auto-focus area you can accurately maintain on the subject. A smaller focus area means the camera looks for a subject or target over a smaller area, and thus has less data to process. If you use the entire frame for focus, it may work fine in some situations, but if you are having trouble, try reducing the focus area to a smaller group or area of the frame. If the subject is large relative to the focus area, the camera will have a much better chance of sharp focus.
The second way you can help the camera is by making sure the subject is large enough in the frame. Sure, we often encounter distant subjects. But the subject needs to be large enough in the frame to be a target rather than just a few pixels. Try to have a subject occupy at least one-third of the height and width of the frame. If it is smaller or more distant, consider using a longer lens or try to move closer. If the subject is small within the frame, you will much more likely need to use traditional focus methods rather than face or eye detection. Don’t get hung up on trying to make the eye focus detection function work – the point is to focus on your subject and get a good photo no matter what techniques are required.
Autofocus generally works by utilizing contrast within the area you’ve chosen. But if your subject has little contrast or is undefined, your camera may struggle to identify the intended target. There are a number of reasons why you may have low contrast (and cameras tend to cope with this remarkably well), but be prepared to step in and help if necessary.
Conventional wisdom dictates you should always focus on the eye of your subject. And that’s true – you do want the eye in focus. But in many cases the eye is too small, or moving too quickly, to be a good focus target. In this case, you can choose a different focus target within the same focus plane and still capture that subject in sharp focus.
In this photo of a rider on a horse, the eye of the rider and the eye of the horse are small and moving rapidly. Another problem is that, by focusing on the eye of the rider, the resulting depth of field will likely throw the horse’s head and eye out of focus. The solution? Select a good target that is easier to follow, in this case perhaps the knee of the rider, the rider’s hands, or the front edge of the saddle. Even with fast movement, the knee of the rider is relatively easy to follow and the horse’s eye and the rider should both be reasonably sharp. The angle of the horse and rider relative to the camera makes a difference. If the horse is running, say, right to left in front of you, all within the same plane, it’s much easier to keep everything in focus. If it’s running right at you, depth of field will be more of an issue, since the horse’s head and the rider are not the same distance from the camera.
For photographing birds in flight, there are some similar strategies. Focusing on the eye of a moving bird can be difficult, but if the neck or shoulder of the bird is in the same focus plane, it makes a much easier focus target. Even if the bird angles slightly to the side as it flies, the bird’s head and its nearest wing will remain in focus.
What does it mean to have a good focus target? While focus generally relies on contrast, there’s more to it than that. Focus tends to be faster and more accurate with a good target. A good focus target is one with contrasting elements, adequate lighting and sufficient size to fill a meaningful portion of the frame. A poor target tends to have irregular shape and texture, relatively little contrast, low lighting (and therefore minimal contrast), or an indistinct pattern. If you have a poor focus target, auto-focusing will take longer and/or be less accurate, so you may need to identify an alternate focus target.
Let’s consider some examples:
When I photograph a subject or genre, I have a very specific focus target. I’m not focusing on a group of trees or flowers – rather, it’s a specific tree trunk, flower or plant. The closer I get, the more specific that focus target becomes, coming down to a specific petal or part of the stamen of a flower, the near corner of the eye of an owl, or the eye rather than the muzzle or nose of a dog, etc.
I also want to be aware of hyperfocal distance – the distance at which I can focus and make the entire scene sharp, including my subject and the background. With a 24mm focal length on a full frame camera, I can shoot at an aperture of f/8 and the entire scene will appear in focus if the camera focuses on a target 8 feet away. In this case, everything from 4 feet to infinity is in acceptable focus. I’ll typically use f9 for a little extra cushion on my depth of field.
I’ve memorized several focal lengths and the related hyperfocal distance so I can shoot at 24mm, 35mm, 50mm or 70mm and make a reliable guess on hyperfocal distance, which allows me to predict which parts of the scene will appear in focus. These settings are a starting point, and I adjust depending upon my subject and where it is located within that range.
For wildlife, in most cases you want the near eye to be in sharp focus and to contain a catchlight. Depending on the position of the bird’s head, depth of field may need to be increased to bring both eyes into relative focus. But it may not be possible to capture a large flying bird that is in sharp focus from one wingtip to another. So make sure the eye and head are sharp even if your depth of field is relatively shallow. The same would be true for insects, like this butterfly:
Sometimes, however, your subject is partially obstructed, or in such low light that your camera fails to focus reliably. Fortunately, there are strategies you can use for those situations.
My first choice is to look for an alternate focus target near the same plane. For example, I might focus on a tree trunk or branch near a small bird. I may try a smaller auto focus area, such as a small group or single point instead of the entire frame. I might focus on the wing or feet of a bird if that presents a better target than the head. Or I may override auto focus and use manual focus to zero in on my subject. I find that once focus has been achieved, the camera is remarkably good at maintaining that focus on a difficult subject.
In the following image, I focused on the trees and waited for the birds to reach that approximate area in order to have both the trees and birds in focus in the pre-dawn light.+
Many photographers have questions about focusing on fast-moving subjects. Certainly, the degree of difficulty goes up in these situations, but the principles are the same.
Of course, we all like our subjects to be isolated, with the clean backgrounds that are associated with a fast lens and shallow depth of field. But if your subject is completely out of focus and the image in your viewfinder is a blur, your camera will take longer to focus because it can’t readily identify your subject.
However, if you can pre-focus in the general vicinity of your subject, you will likely make it a lot easier for your camera to pick up a fast-moving target. Cameras can make small focus adjustments almost instantly, but large changes in focus distance take much longer. It will usually help if you focus on a fast-moving subject before you are ready to make a photo. Pre-focusing allows the camera to find the subject and will make it easier to maintain focus as the subject gets closer. So try to lock focus on that big bird as soon as possible, and then maintain it as he gets close enough for your photo.
If you are trying to focus on a fast-moving subject, make sure it is large enough in the frame and can be clearly identified and separated from the background. It’s very difficult to focus on a small songbird flying across a cluttered, wooded background, but much easier to focus on a wading bird as it launches into flight or drops to the water for a fish.
Practice, practice, practice! With a difficult subject, it’s amazing at how much improvement you will see with lots of practice. I’ve seen photographers start the week struggling to capture birds in flight, but by the end of the week they are nailing a very high percentage of their shots. Even if you are photographing slow-moving subjects or landscapes, practicing focus and concentrating on your focus targets will provide sharper images.
Eric Bowles is a former president of GNPA, a professional nature photographer, and director of Nikonians Academy. He leads bird photography workshops for Nikonians, Chattahoochee Nature Center and Georgia Audubon in addition to his own programs.