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The focus itself may be adjusted in a variety of ways. Larger view cameras and the like slide the lens closer or further from the film plane on rails; on smaller cameras, a focus ring on the lens is often rotated to move the lens elements by means of a helical screw. Other systems include levers on the lens or on the camera body.
Macro or close-up modes tend to direct the camera's focus to be nearer the camera. They may shrink the aperture and restrict the camera to wide-angle in an attempt to broaden the depth-of-field (to include closer objects) – this last mode of operation is often known as Super Macro. Movie mode allows a still camera to take moving pictures.
Focus remains locked until the shutter release is pressed fully or the button released. Manual focus is initiated by a button on the top plate of the camera. Focus is adjusted by reading the focus distance from the top-mounted LCD and adjusted with the "+" and "-" buttons. A single button can be pressed to lock focus at infinity.
Focus can be adjusted manually by the photographer or automatically by an autofocus system. The viewfinder can include a matte focusing screen located just above the mirror system to diffuse the light. This permits accurate viewing, composing and focusing, especially useful with interchangeable lenses.
In photography, manual focus override, also known as full-time manual focus, allows manual intervention in the autofocus acquisition process simply by turning the focus ring on a photographic lens. There are a number of technologies used to implement this feature.
Manual focusing is usually a requisite for professional filmmaking, because autofocus systems may focus on undesired objects, or fail to adjust quickly enough to sudden changes. The job of the focus puller then is to adjust the focus onto different subjects as well as maintain focus during movement of the camera relative to the subject.
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An autofocus (AF) optical system uses a sensor, a control system and a motor to focus on an automatically or manually selected point or area. An electronic rangefinder has a display instead of the motor; the adjustment of the optical system has to be done manually until indication.