When autofocus is in effect, you can select the AF-area mode depending on whether you want the camera to focus on the subject in a single focus area (single-area AF), or to follow the subject as it shifts from one focus area to the next (dynamic AF).
In single-area AF, the choice of focus area is in your hands. If your subject is moving erratically, or if you are experimenting with a variety of compositions, it may however be difficult or impossible to select the focus area using the multi selector. In cases such as these, dynamic AF can be used to give the camera control over selection of a new focus point.
When dynamic AF is used with single-servo autofocus, the focus area can not be selected using the multi selector. Instead, the camera continually assesses the distance to the objects in all five focus areas, and automatically chooses the focus area containing the object closest to the camera. This combination is useful when your subject is always positioned closest to the camera but you are trying out a number of different camera positions to find the best composition.
When dynamic AF is used in combination with continuous-servo autofocus, the camera measures the distance to the subject in the selected focus area when the shutter-release button is pressed halfway to initiate autofocus. It will continue to focus on this subject as it moves from one focus area to the next. The multi selector can be used at any time to choose a new focus area. This combination is useful when your subject is moving erratically and manual focus area selection is too slow or cumbersome.
AF Area Mode
Dynamic Area AF
Single Area AF OK