While some of the least expensive digital cameras have only automatic focus, meaning the camera does all the work on bringing your subject into the best possible focus, most SLR digitals offer three different focus modes: manual, single auto focus and continuous auto focus. All three of these will be addressed here.
With manual focus, the camera stays out of the focus equation and you, the photographer, make all the decisions regarding this. This is done by setting different buttons or actually using an attached focusing ring that rotates on the camera lens. For those who like to have complete creative control of the finished product, this is the best focus mode.
In single auto focus mode, the camera automatically focuses when you press the shutter button either all the way down to shoot a photo or half way down to lock the focus. This mode is useful when shooting static objects.
In continuous auto focus the camera continuously focuses on the objects in the photo. In this mode the camera continuously corrects the focus as the objects distance from the camera changes. This mode is useful when you shoot photos of moving objects such as a race car...