The dedicated 1.4x APO Teleconverter features a high-performance 5-element/3-group optical design, and it is optimized for use with long 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 and current Nikon AF cameras (except N60/F60 models). They are ideally suited for use with the 70-200mm F2.8 APO EX HSM zoom lens; providing normal exposure and autofocus function, while maintaining its high optical performance.