He seems to have a 1DX. And the 1.4x is the first one mounted. Not sure if that matters. I tried my 5D3+1.4x+12mm+100-400L @400mm and it did not AF. Even manual focus was not possible. My 12mm macro extension tube is Kenko but I don't think that is the problem.
I tried the 2XIII and 1.4XIII with a 13mm extender a friend of mine has. My 1D IV said Error!
My 5D III said, OK, but I can't focus. And My friend's 7D said...Error.
The Photo is actually just the 2X on my 400mm with my Mark IV
The Canon 12mm II just arrived. My 5DIII won't focus either manually or AF with the 1.4x III -12mm - 2x (or vice versa). What am I doing wrong? Does anyone want to buy a 12 mm Canon II extension ring, 1 day old, used twice?
I guess this is one for Alex to field...