Focal Length

Focal Length

The focal length of the lens, usually measured in millimeters, is marked on the front or side of the lens. Focal length is the distance between the lens and the film, sensor or pinhole (depending on the type of camera) when the lens is focused at infinity. Focal length determines how the lens will magnify distant objects. For example, telephoto lenses have extremely long focal length and can magnify objects at a great distance from the camera.