#Focal Length

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Focal length is a number expressed in millimeters (mm) that describes a lens’s field of view and magnification. The number is the distance from the point where the light converges to form a sharp image when focused at infinity to the sensor or film plane. A smaller distance in millimeters equals a wider angle of view and a larger distance is a narrower angle of view. For example, 16mm is a very wide angle of view (a wide angle lens) and 400mm is a narrow angle of view with more magnification (a telephoto lens.)