What's Auto Focus Modes and When to Use It?

1. Single Area Focus
   
   Focuses on the subject, normally in the center of the screen. Some cameras allow repositioning of the focus area anywhere on the screen.
   
   When to use: This should be the default setting and most accurate as you (not the camera) decide where to focus.
   
   
2. Spot Focus
   
   Focuses on a small area in the center or otherwise (if camera allows).
   
   When to use: Focusing on small objects or birds and wildlife. For example, a bird might be on a tree and if you select single area focus, you camera might focus on the leaves and branches rather than the subject.
   
   
3. Multi Area
   
   Camera automatically focuses on subject by evaluating multiple areas. The number of areas and it's position vary among cameras. A camera may evaluate many areas, but only select one or more area to focus on, depending on the scene.
   
   
   
   When to use: When you want the camera to decide which area to focus.
   
   
4. Focus Tracking
   
   You select an area and the camera will automatically track the subject as it moves or when you recompose your shot.
   
   When to use: When trying to focus on fast moving subjects or pets.
   
   
5. Face Detection
   
   Camera automatically detects faces to focus on. Some cameras allow up to 15 faces to be detected.
   
   When to use: When taking portraits or group shots.
   
   
6. Face Recognition
   
   Some cameras (e.g. Panasonic Lumix GH1) have face recognition, where you take a picture of your wife/girlfriend/husband/boytoy and then key in their name, and the next time you photograph them, the camera will automatically detect their faces and focus on them. When you're taking a group shot, the camera will also focus on recognized faces rather than "the rest". Presumably, the camera also allows you to delete recognized faces otherwise ...
   
   When to use: Anytime you get an opportunity.
   
   
7. Manual Focus
   
   You set the focusing, sometimes with the camera's help.
   
   When to use: Whenever you like.