Many consumer digital cameras have more than one focusing mode. When using an automatic mode, focus is locked whenever the shutter-release button is pressed down half-way.
Correct use of the two-step shutter button is key to obtaining proper focus. Other factors also come into play such as the amount of light falling on a subject, the amount of contrast in a scene and the motion of a subject.
Many cameras come equipped with an auto focus assist lamp that helps the camera focus better when lighting of a subject is low or lacks adequate contrast. A focus assist lamp is most effective when photographing non-moving subjects that are in fairly close range.
The LCD or electronic viewfinder indicates when and where focus is locked. A visual indicator, such as a small lamp or change in color of the focus indicator, confirms when focus is achieved. Digital cameras may also have an audio sound indicating locked focus.
Single (or one) area focus — Camera focuses on a subject in the central area of the screen. Focus adjusts according to the distance of the subject. This focus mode is usually the most accurate because you, not the camera, decides where the camera focuses.
Continuous autofocus — Focuses continually on a subject. Continuous AF can be useful, though not always perfect, when shooting slow moving subjects. On digital cameras with video capabilities, continuous AF is usually the default focus mode.
Spot focus — Camera focuses on a very precise center area of the screen.
Multi area focus — Camera automatically focuses using multiple focus points. The focus positions change according to each subject, focusing on a number of objects within a scene. This mode can be less accurate than single area focus.
Face-priority AF — Face-priority AF is a digital camera detection program that scans for facial details. It controls the auto focus operation based on the location of the detected face in the scene. It may give exposure priority to the face as well. Some digital cameras let you lock focus on a specific face. If the subject moves, or the photographer recomposes the picture, focus remains on the subject’s face.
Prefocusing can be effective when there is a pre-determined, similar distance between the camera and subject. Focus is fixed until you press the focus button again or switch to a different focus mode. Prefocus allows you to lock focus on a subject, then recompose. Digital cameras have different methods of prefocusing, so check the manual.
Manual focus area — Focus on a portion of a scene when not centered in the frame. This method is useful for close-up and macro shots.
Focus ring — Focus manually, from a few feet to infinity, by turning a focus ring near the lens.
Focus button — Depress a manual focus button and rotate a dial until the subject is in focus.