Understanding Focusing Options in Digital Photography - dummies

Understanding Focusing Options in Digital Photography

By Julie Adair King

Digital camera focusing systems range from incredibly simple to amazingly complex. Few people need all the focus-related settings found on pro cameras. (Even fewer people understand how to adjust those settings in a way that makes sense for their subject.) But neither should you buy a camera that offers you no control over focusing, which is the case with some cellphones and basic point-and-shoot cameras.

To help you find the right balance, here’s an introduction to focusing features:

  • Focusing method (automatic and manual): Even the best AF (autofocus) systems have trouble with some subjects, such as highly reflective objects. So the option to switch to manual focusing is a plus.

How manual focusing is implemented is also important. In most cases, you adjust focus by turning a ring on the lens — easy peasy. But some cameras instead require you to select a menu option and then enter a focusing distance, which is not only time-consuming but also requires an accurate sense of how far your subject is from the camera. Still, this form of manual focusing is better than none.

  • Focus point selection: Most cameras are set by default to focus on the closest object, which causes problems if that object is not your subject. A good option is a camera that enables you to select from several focus points located throughout the frame. Some cameras (and lenses) also offer an infinity setting, which sets focus at the farthest point possible.
  • Face/eye/smile/blink detection: These features are designed to simplify portrait photography. Face detection searches the frame for a face, and if it finds one, automatically sets focus on that person. Sometimes you can choose which face in a group portrait to use as the focusing target. Models that offer eye detection narrow their search to specifically target the subject’s eyes, which are of primary importance in most portraits.

Taking these features one step further, some cameras offer smile-and-blink detection. In this mode, the camera tracks a subject’s face and then snaps the photo automatically when the person’s eyes are open and smile is widest.

face-detection
Face detection is a feature that automatically looks for and sets focus on a face.

These features aren’t foolproof; most face-recognition systems don’t work unless your subject is facing forward, for example. And as for smile-and-blink technology, it does the trick only if everyone in the portrait displays wide smiles and bright eyes at the exact same moment. So the best way to ensure that you get a great-looking portrait is to snap many different images of your subject.

  • Single and continuous autofocusing: Single autofocusing refers to the standard autofocusing method used on most cameras: Focus is locked when you press the shutter button halfway (or tap the touchscreen). This system works fine for still subjects, but for moving subjects, you’re better off with continuous autofocusing. When you use this feature, you select an initial focus point, and then if the subject moves, the camera tracks that movement, adjusting focus as necessary until you take the picture.
  • Number of autofocus points: Generally speaking, higher-end cameras have more focusing points than lower-priced models. The difference is most important when you shoot rapidly moving subjects and rely on continuous autofocusing: In this mode, your subject will stay in focus as long as it remains under one of the active focusing points. The more focus points, the better the chances of that happening.

However, because analyzing all the focusing data can slow the system somewhat, a good camera will enable you to choose how many of the available points you want to activate.

  • Type of focusing points: If a camera offers cross-type autofocus points, it gets extra credit. Cross-type points improve autofocusing performance because they look for focusing information in four directions: up, down, left, and right. Normal focusing points work only in the vertical direction.