!@ Sigma APO Teleconverter 1.4x EX DG for Pentax Mount Lenses 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. Sigma APO Tele Converter 1.4x and 2x are dedicated Tele Converter lenses, which should be used only with the listed lenses. The 1.4X Convertor will fit the following lenses 180mm f/3.5 APO MACRO EX HSM - MF 300mm f/2.8 APO EX HSM - AF 300mm f/4.0 APO MACRO - MF 400mm f/5.6 APO MACRO /HSM - MF 500mm f/4.5 APO EX HSM - MF 800mm f/ 5.6 EX HSM - MF 70-200mm f/2.8 EX HSM - AF 70-210mm f/2.8 - MF 50-500mm f/4-6.3 APO - MF 100-300mm f/4 EX HSM - AF 120-300mm f/2.8 EX APO - AF 300-800mm f/5.6 EX APO - MF Will also fit the following Orginal Nikon AF Lenses 300mm f2.8 AF-S - AF 300mm f4.0 ED AF - MF On the lists, the lenses marked "AF" will retain auto focus operation when used with a Tele Converter. The lenses marked "MF can only be used for manual Please refer to the manufacturers Teleconverer Matching List for an updated compatability chart. http://www.sigma-photo.co.jp/english/acc/condaitr.htm The Sigma APO Teleconverter 1.4x EX DG for Pentax Digital SLR Cameras is a dedicated APO teleconverter that can be mounted between select lenses and the camera body to increase the focal length by the power of 1.4. The multi-layer coating reduces flare and ghosting, which is a common problem with digital cameras. The lens also offers maximum magnification without any variation in the minimum focusing distance. Compact and lightweight, this teleconverter can convert your lenses into longer focal-length lenses, so you don't have to do a lot of unnecessary footwork. A case for the lens is included. Low Price - Click Now!