5D III with 2X extender on a 2.8 70 - 200 Lens

[mStevens]

I cannot find the threads that discussed issues using an extender on a 5D III. It had something to do with aperture 8.0. Can someone refresh my memory on what that the issue was?

[neuroanatomist]

No worries for you. A max aperture of at least f/5.6 is needed for AF, and an f/2.8 lens with a 2x TC is f/5.6 (the aperture you set is irrelevant, AF is done wide open).  Do note that a 2x TC will slow down the AF by 75%, though.

[mStevens]

Thanks for the quick response. I am shooting pics of my daughter's soccer tournament game today and at the first game i did notice a lag in the focusing. I did not know about the reduction in the AF. I am going to her second game in a few moments and I think I will leave the extender in the hotel room. I kind of regret bringing my FF on this trip. I think next time I will use my crop frame camera.