[Jose]

So if I put a 2x extender in a 200 mm lens it does not become a 400mm focal length lens? The image is 2x larger? Does not a 1.6X sensor does the same other than preserving the original f stop of the lens?

And yes, I do concur tha the original lens focal lens remains the same but the use of the 1.4X extender or the 1.6X sensor alters its original focal lenght.