I just bought my first M; a late M2. I bought a summaron 35mm f3.5 with it. But I think there may be a problem. The viewfinder shows three sets of brightlines; what I assume to be 35mm (the biggest, almost to the edge of the viewfinder), 50mm and 90mm (the smallest). When I attach the 35mm lens, the lines snap down the the middle size. Is that right? That feels like what it should do with the 50mm. Thanks for your input; it's my first rangefinder, so I'm alittle new.