all good suggestions. there is one more lens you might want to try is the Sigma 400mm 5.6 APO Macro, it's hard to find it now, you can google it, there are some reviews on the internet, it should be a very good alternative choice, if you are lucky, you can find it for about $400-$500


Quote Originally Posted by Fast Glass
Or taping the pins trick wil give you poor AF performace in lower light.

John, I tried that trick on my 400mm 5.6 with the 7D, not very happy with the results, it hunted a lot even in good light. there is no cheap solution if you want something longer than 420mm and still AF on the non 1D body[]