Originally posted by kamis68 Hi,
Does anyone have experiences of Sigma EX 1.4x APO DG teleconverter with Pentax smc DA* 300mm f/4.0 ED (IF) SDM lens and K20D?Any problems with autofocus?What about Kenko 1.4x?Or are there any other compatible converters available that will (not should) work?
Thanks a lot for your comments/help in advance!
the sigma teleconverter is probably NOT compatible with the DA 300 F4 due to the fact that the front element of the sigma TCs extends into the rear of the lens.,
You need a recess at the rear of the lens 35mm in diameter 14 mm deep to accept the sigma TC
aside from that the sigma TCs do not support SDM so you would be MF only, assuiming it mounts at all.
Aside from older TCs that were initially released for the Power Zoom lenses in the early 1990's, you can also use the SMC-F 1.7x AF TC. This will not drive SDM or even the lenses own screw drive, but the TC does have its own focusing elements, therefore providing a limited range of AF once you manually focus close to the correct distance