I am going to Costa Rica. I just started a birding class. My lens 70-200L is not strong enough. I am not sure how passionate I will be about wildlife photography but I want to purchase a lens. I have a Canon 7D. Some photographers in my class have suggested I switch to Nikon. Here is my situation. I would like a good lens but I have a hard time with a heavy lens. Should I buy one of the following or an extender 1.4 or 2.0. I do not like the idea of compromising sharpness. Will I be unhappy with the extender? I am not a professional photographer and this is not my occupation but I do enjoy sharp pictures. Canon: EF 100-400mm f/4.5-5.6L IS USM EF 400mm f/5.6L USM EF 400mm f/4 DO IS II USM EF 400mm f/2.8L IS II USM Extenders?