Auto Focus

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A system used to automatically focus a camera's lens on the subject.

This is usually done by emitting an ultrasonic sound wave which is reflected off the subject allowing the camera to work out its' distance from the subject or by emitting infra red light to achieve the same information. The lens is equipped with a motor which will turn the focus ring to the desired setting and bring the subject into focus. Most modern SLR cameras use either single or multiple optical sensors to determine focus as well as reflected light values for exposure control.

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