Just got the Kenko Pro 300 1.4 and 2X DG teleconverters for Nikon "AFD" lenses. They work fine with my Nikon 70-200 f2.8 vr lens, but what I really got them for was my Sigma APO 500mm f4.5 EX DG/HSM tele. I realize the 2X is probably good for manual focus only, but the 1.4X doesn't want to lock focus on anything other than a perfectly stationary object (camera and lens , tripod mounted). I think the 1.4X/500mm combo should be able to autofocus OK at 4.5 (or even 5.6), but it hunts all over the place (not good for small birds) and sometimes gives up completely. Does anyone have any experience with this setup, or can someone suggest an alternative teleconverter that does autofocus with the Sigma 500 f4.5 HSM? I'm using Nikon D80 and D300 bodies with the same result. Any help will be appreciated. dstretch
I have the Sigma 500mm and Kenko 1.4x combo and don't seem to have a problem on my D70 if the light is reasonable. I've only had the Sigma for a few weeks so I'm looking forward to some good light!
Thanks for the response, RezMole. Is your Sigma the "DG/HSM" (latest) version? My Kenko converters are marked "AFD" on the barrel, and I'm thinking that maybe I should have gotten the "AFS" version, if available. The Sigma focuses great manually with the 1.4 and 2X converters. I would prefer autofocus for the smaller birds, though.