Something else to keep in mind is that on your crop sensor a 200mm lens will be the equivalent of 320mm, and a 300mm will actually be 480mm. When I started out I used the 70-300 on the 60D for a lot of wildlife shots. Sometimes it will come up short ...
I also have the 100-400L and the 2xIII. I rarely use that combination when shooting with the 5dIII as you are very limited on apperature. I don't know which body you are using, but you will be at f/9 when shooting at 400mm on the lens, so you will ne...
