Hi guys I have a 1200D and use an EF 100-400 LS lens, i have recently acquired a Canon 1.4x extender and also a Kenko version, 1.4x, which i wanted to use on the 100-400 lens. I have found this combination of either extender doesnt work on the 1200D, no AF I have tried the combination on a Canon 5D mk 2, still wont auto focus, I updated the firmware on this body to the latest version but this still didnt AF I have also the 75-300 canon EF lens, the kenko extender works on the 1200D in auto focus but the canon version wont fit the 75-300 as the lens on the canon extender is too prominent Can anyone advise what body will work with the canon extender plus 100-400 and auto focus. someone told me the mk3 5D works but i dont have access to try the combination. Plus im working on a tight budget thanks for any information David
I can't help with experience on the lens here, but its more of a physics issue, you have a slow long zoom and by adding the extender you are loosing stops of light, on top of that. You now are trying to use a f8 or f9.5 lens with auto focus, there just is not a lot of light to work with. Seems like some higher end bodies work that have better more modern auto focus systems, and I noticed a few people saying on mid range bodies had live view focusing work ok. I recommend sticking to fast 2.8 lenses if you want AF performance with an extender. That said I don't think the mark 3 is much of an upgrade to the mark 2. I would save and get the mark 4 if you upgrade.
