Autofocus (AF) is an optical system that uses a sensor, a control system and a motor to focus on an automatically or manually selected point or area. The process of autofocusing generally works as follows:

  1. An autofocus processor (AFP) makes a small change in the focusing distance.
  2. AFP reads the AF sensor to assess whether and by how much focus has improved.
  3. Using the information from (2), the AFP sets the lens to a new focusing distance.

Autofocus systems can be found on film and digital cameras.