My original Nokton (the one for the Prominent) has a cemented pair at the front which is liable to start splitting (but mine is fine). The peculiar mount with compur central shutter behind plus focussing mechanism in the camerabody has prevented me from getting a cheap adapter, so except for film where it works fine, no chance to really put it through its paces, Reputedly its f2 Ultron brother is better (=sharper&more contrasty).
p.