From a falconry display.
5D3 300mm f2.8 IS mk1 plus 1.4x Kenko TC.
The second one is awesome.
The owl was only about 9 inches in height (coulda just stuck it in my pocket!) and was used for a quick display for small kids - flying from its perch onto the kids' outstretched arms. I took tons of shots but only got a couple that were sharp. I think the Kenko TC slowed down the focus speed/reaction time of the 5D3 and 300mm.
I was using the combo to help decide if I should get a 500mm mk2. Overall the 300mm on its own is terrific but with the TC I wasn't completely thrilled with the results from the afternoon; some good, many bad. I hired the 500mm for an airshow a couple of weeks back and was amazed at the quality. Clearly you wouldn't use the 500mm for falconry due to the proximity of the action but I wanted to see how snappy the 300+1.4x combo would be. Might be acceptable to some, not me. Sigh
, that'll be more money on this hobby....