« on: February 07, 2014, 12:35:02 PM »
My experience with the 300/2.8 II + 2xTCIII having poor AF speed and hunting on the 7D has been duplicated by others. Many of us have found poor inconsistency of AF in general. Lensrental has somewhere on its blog showing the AF consistency of the 7D being far worse than the 5DIII.
The series II telephotos have a different feedback loop system from the series I and required the series III TCs to be developed. I have no idea how the series I telephotos AF perform with the 7D plus TCs. By all accounts, the 300/2.8 I takes an IQ hit with the 2xTC.
Ok, I expected some IQ degradation with a 2x TC anyway. I think I will go with the 1.4x for a start. I hope this will still give some great quality pics.