JESSOP MC 2X N/AFs TELE CONVERTER Extends the focal length of your existing telephoto lens by a factor of 2, bringing the subject closer. Fully multi-coated optics to reduce ghosting and flare. Autofocus is maintained for lenses with a maximum aperture of F4 or faster (e.g. F2.8), a limit set by the Canon body. Slower lenses may be focused manually using the camera's focus confirmation indicators. Will give its best performance when used with prime lenses.