 When used on a digital EOS body with a field of view compensation factor of 1.3x, such as the Canon EOS-1D Mark IV, it provides a narrow field of view, equivalent to a 390 mm lens mounted on a 35mm frame body.With a 1.6x body such as the Canon EOS 650D, it provides a narrower field of view, equivalent to a 480 mm lens mounted on a 35mm frame body.This lens is most commonly used by sports and wildlife photographers, but is short enough to be use for extreme close-up portraits.