I was experimenting with the above combo and the 5D3 locked up on me every time I took a shot. To unfreeze the 5D3, I had to remove the battery. I had tried this combo once or twice before without any problem (the 5D3 knew the Kenko presence and reported the correct focal length of 588mm f5.6), but had not had a chance to compare the AF performance and IQ with a straight Canon 2X ii. Has anyone experienced this lock up issue?
I have also used a Canon 5D3, 300f2.8 IS, 2Xii, and Keno 1.4x. AF works fine for static object, but IQ is not great, so not a good combo.
