When is 50mm NOT 50mm?

Definitely -- a 50mm lens is ALWAYS a 50mm lens -- that's physics.  BUT, I guess the actual question should have been what is the effective focal length of the lens?  When selling an E-mount lens is Sony quoting the actual focal length of the lens OR the effective focal length on their NEX system?

Is it really as simple as a 50mm lens is always a 50mm lens?

--
Stephen Lucchetti