So I was daydreaming about the 200-400 lens today and something occurred to me. Without the built in 1.4 extender "activated" the focal length is 200-400 and with the extender activated the focal length is 280- 560. So does that mean that since there is an overlap from 280-400 that you can get to that range of focal length two ways: one way with the extender activated and the other way without? If this is true is there any difference in the image depending on how you get to that overlapping focal length? For example I know that with regular (not built in) extenders like you 2x, you lose a stop of light when you attach it to your lens. Does activating the built in extender affect your maximum aperture? Although the answers to these questions will never affect me in real life (as my wife would kill me if I spent this much on a lens), I was curious to know.