Focal length multiplier: Most sensors used in DSLRs have a smaller area than the surface of 35mm film. Yet, for historical and convenience reasons, focal lengths are still expressed in the 35mm format. This means that each camera’s effective focal length will be different than the one listed on a lens. To calculate the effective focal length of a lens and camera combination, the user must use the focal length multiplier of the camera. Canon’s entry-level cameras’ multiplier is usually 1,6, though their higher-end models do not have a multiplier. Nikon, Sony, and Pentax usually have a multiplier of 1,5, while Four thirds systems (such as Olympus and Panasonic) have a multiplier of 2. As an example, a 50 mm lens on a Nikon camera would have an effective focal length of 75 mm, while a 12-48 mm zoom lens on a Four thirds system would have an effective reach of 24-84 mm.