Canon extenders on 3rd Party lenses

[jamesward93]

Does anyone know if the canon extenders work on 3rd party lenses?

I have the x1.4 extender and am considering getting a sigma 300mm 2.8 (more in my price range than a canon equivalent) i am presuming they will work together in as far as getting the extra reach (i may be wrong), i am not so confident in the AF working though

Has anyone tried this? did they work together?

 

[HoppyUK]

You have a Canon 1.4x extender? It will work fine. 300mm f/2.8 becomes 420mm f/4.

 

[jamesward93]

yes its the canon extender. OK sounds good, I know that i would loose a stop but not a major problem for me, my main concern is that the AF will still work.