Sigma 1.4x EX DG APO Tele-Converter for Pentax AF Cameras

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