sounds like you have the k mount pentax I'd buy a black k2 like the one at keh . Personal bias here but I'd say the k2 is every bit as good as the nikon you're looking at priced competively and pentax lens are just as good as nikons but priced better.I remember a thread on rff about an adapter for the 50 1.4 to leica m mount that got a lot of interest.