Tomorrow is the day I'm finally going to get my Nikon D5100.
Already got a vintage Pentacon 50mm f1.8 lens for it, found one in a drawer while looking for something completely different. Well, it's M42 so that means, I can't focus to infinity with the adapter plate, but as some people already pointed out in an DSLR forum, it will be okay for portraits and macros, as it can still focus to roughly 1m / 3ft.
But on the other hand, because I can't focus that far, I now can focus even closer than the 0.33m/1ft which it says on the lens itself. Should be a nice macro/portrait/heavy bokeh type of lens.
Example shot from someone else(pretty much the range I will be using this lense)