No 500mm on the list?


I assume you mean the 600mm II that is coming out. The old 600mm is to heavy, I wouldn't recommend it. You were saying the 400mm is cheaper than the 600mm so I am not sure if you are thinking old versions or new versions here.


The 500mm with a 1.4 is going to get you out to 700mm. The IQ loss with the 1.4 on the 500mm is going to be about the same IQ loss on the 300mm with the 1.4. It is going to be very slight yet usable. I own both the 300mm F2.8 and the 500mm F4 and it is a very nice combination.


If you only want the 600 for small birds and nothing else, it wouldn't be a bad option provided were talking about the new 600mm II version. The new version will weigh about the same as the old 500mm. My 500mm I can hand hold. After carrying the 500mm around for almost two years, I know I wouldn't want any more weight than I have now. (when I say I can handhold the 500mm I have to say I am very thankful for IS if the animal is standing still, steady I am not)


You might have the thought that you can deal with the weight because you will have a tripod or monopod. That would be great if your in the back yard at the bird feeder, or maybe hike somewhere and set up a blind. With wild life often shots present themselves, spending one minute putting on the monopod or setting up the tripod looses the shot. I think with the heavier lenses you may miss allot of opportunities.


I don't like the idea of the 2x on the 400mm. I haven't seen a lens yet that I think the IQ is good enough with the 2x. You will be better served getting as close as you can to what you need.


Just my thoughts....any direction you go you will have an awesome lens.