I have one or two ( maybe silly ) questions... as I'm considering to buy one lens from Four Third system, I know that I must have a proper adapter for my mount. If I'm not wrong only the EM-1 can use this lens without adapter in MIcro Four Third System . So, the question is... Which adapter to buy, I see several of them with different names and numbers, and other question is .. Does adapter changes the focal length of the lens which is mount on ?