I am still going through files from past photo trips. Now that I am retired I have time to go back and work on images I had not gotten to adjust before. Work always seemed to get in the way. This is a series of images of a Red-shouldered Hawk take-off from a small branch at Ding Darling National Wildlife Refuge in Sanibel, Florida. I was using a 400mm DO lens with a 1.4x Teleconverter on a Canon 7D (for an effective Full Frame Camera equivalent field of view of ~896mm). Many times at Ding Darling you see interesting photo opportunities but the subjects are quite far away. So it is fun to try different ways to photograph distant subjects. The more you try different techniques, the better your results and are more predictable. With a 1.4x teleconverter I would stop the lens down 1 more stop than I would usually use. For a 2x teleconverter I would stop the lens down 2 stops more. With a 1.7x teleconverter I would also stop down 2 more stops than usual. Yes I actually found a 1.7x teleconverter for Canon lenses.
I was surprised it kept focus on the hawk and not on the branches as I was tracking the hawk.