2x ex dg apo tele converter the dedicated 2x apo teleconverter features a 6 element5 group optical design and it is specifically designed for use with longer telephoto and telezoom lenses the high performance optical characteristics of these teleconverters maintain the optical performance of the compatible lenses with which they can be used using 10 pin electrical interfaces there is no loss of autofocusing speed when these teleconverters are used with compatible hsm type lenses for canon sigma