Here we have the Feisol and Gitzo shooting a 300/4 AFS + TC17 at 500mm. This is why I always suggest a Series 3 class (32mm legs) for this lens. If you own this lens you *will* be shooting a TC. If not now, eventually. It is just irresistable. Almost all of us that own this lens really want to own a 500/4 or 600/4; we just can't afford it. We'll all be at 420mm or 500mm sooner or later.