The Nikkor 5cm F1.5 and Canon 50mm F1.5 are based on the Sonnar, but are not "exact" copies. They use different glass and are 51.6mm focal length for the Leica standard. I have two early Nikkor 5cm F1.4, but not an F1.5. The early F1.4 lenses look a little closer to the Sonnar than the later ones.