Tuesday, November 18, 2008
10 Tips For Better Autofocus
3 Change Your AF Point
Sure, we’d all like the latest and greatest of the newest cameras, but until we can afford that new purchase, we need to understand how to get the best from the equipment that we do have. Every time that I purchase or test a new camera, I always take it out and play with it before I have to use it seriously. I want to know the camera’s idiosyncrasies regarding autofocus and other controls. It’s important to work with the camera in your hand and get the most out of it rather than worry that it can’t do something it wasn’t designed for.
A third option on many cameras is a hybrid. This type of autofocus allows the camera to decide when to use single-shot autofocus and continuous autofocus. This has never been a choice that I’ve liked. It seems like the camera is always choosing the wrong type of autofocus and screwing up my focus as I shoot. I’d rather choose a specific type of autofocus based on the subject and movement of the subject.
Autofocus often has trouble when you’re dealing with close subjects. Depth of field is so shallow that even a slight change in focus can make the difference between a good picture and one for the trash. Very often the camera will choose the wrong point for focus up close. For this reason, many of the best macro shooters use manual focus for close-up work. There’s also a trick to using autofocus up close. Move your camera around and lock focus on an important part of your subject. Keep that focus locked and gently move your camera toward and away from the subject until you have exactly the right spot in focus. Take the picture. Another thing that drives you crazy up close is when the camera starts focusing to infinity. Many lenses have focus limiters for just this reason. If yours has such a switch, set it so that it only focuses at a close distance when you’re doing close-up photography.
8 Faster Lenses Help AF
A fast lens is a lens with a wide maximum aperture, such as ƒ/2.8. If you need fast autofocusing, you need a fast lens. Most zooms are slower lenses with maximum apertures of ƒ/4 or so, especially the compact zooms. If you have an extended range zoom that’s also compact, you can find that the lens speed gets very slow. For subjects such as landscapes or flowers, that’s not a big deal. For fast-moving wildlife, a slow lens can have a big effect on how quickly you can get the animal in focus.
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