A telephoto lens has a focal length significantly longer than the focal length of a normal lens. For a 35 mm camera with a 36 mm x 24 mm format (43.3 mm diagonal), the normal lens is 50 mm and a lens of focal length 70 mm or more is considered telephoto. On the 6 cm x 6 cm format (84.9 mm diagonal) (120 film) the normal lens is 80 mm, and focal lengths above 100 mm are considered telephoto.