The autofocus feature that comes with most cameras makes picture taking easy. But it can ruin your photos as well as improve them. The problem is that the camera usually focuses on an area in the center of the scene you're framing. If your subject happens to be off to one side, oops.
Learn how your autofocus works. On many cameras, you can adjust the setting, moving the focus area off dead center. Then experiment with focus lock. Point the camera at your main subject and depress the shutter release halfway. Hold it there. Move the camera until you have the composition you want. Push the button the rest of the way. Your subject will remain in focus and will be properly exposed. If you become adept at this technique, you will avoid those pictures in which the background is sharp but your main subject is fuzzy [source: Digicam AE-Lock].
Focus lock also speeds picture taking. After you press the shutter to take a picture, there's a slight delay while the camera adjusts the focus. Holding the button halfway down leaves you ready to take the picture instantly, which can be important with action shots. Make sure that you determine how far away the subject will be when you take the picture and lock the focus on that distance [source: Photo-John].