David Pogue's Digital Photography: The Missing Manual

Which Focus Mode?

Just as most cameras offer different ways to analyze the light in the scene, most also offer different ways to analyze the focus of the scene. In essence, you have two questions to answer: where to focus and when to focus.

Where to Focus

All cameras can focus automatically. But SLRs and some advanced small cameras let you override that autofocus—and, in fact, let you indicate which part of the scene you want to be in focus. Here are your options:

• Center focus. Unless you change the settings, most cameras, out of the box, use this method: They focus on whatever's in the center of the frame. And most of the time, that works fine.

  Tip

  Here's an oldie but a goodie. Suppose you don't want your subject to be in the center of the picture, but you do want the subject to be in sharp focus. In that case, aim the camera so the subject is in the center. Half press the shutter button (sounding familiar?). When you hear the beep or see the indicators change, you've locked in the focus. Keep the shutter button half pressed and then re-aim the camera, recomposing the shot so the subject is no longer in the center. Doesn't matter—that person or thing is still in sharp focus. Push down the rest of the way to get the shot.

• Spot focus. On an SLR, you can switch to a spot-focus mode. That's where you see little boxes or + signs arrayed on the scene; using the arrow keys on the back, you highlight the one you want to be in focus.

  So why use this method instead of the focus-and-recompose trick ...