The one that sits on my "R" is the 35/2.5 color skopar mc, there is very little distortion in the finals, the next is the 50/1.5, nokton silver, oh this is a pleasure to use, nice feel and for the close in moment, or that quick action shot it was there, portrait i find this to one i use the most, unless iam at the m/f cameras, then there is the 25/4 snap shot, you set it up max distant, f4 and all is well, having the little finder on the top of the "R" shows just how much is there.
None have let me down.