Leica M3 produced from 1954 to 1968, matched here with a Voigtlander Nokton 40mm lens.

I have shot the M3 before, just not this one. I had not shot this lens before. So, why this match or mismatch? The M3 does not have frame lines for the 40mm (only 50, 90 and 135). Actually none of the Leica M series have frame lines for a 40mm lens. The closest to an exception is the Minolta/Leica collaboration, CL and the CL's sibling the Minolta CLE.  That said, I had heard that the outside of the M3 viewfinder was a match for a 40mm lens. And since I needed to test both, I figured I'd give it a try.

My Take:

I did not do any calibration or specific shots to verify that the 40mm lens matches the M3 viewfinder as reported. It seemed about right based on my shots but honestly the 50mm frame lines on the M3 are so dominate that it was hard get past them to use the full window. 

The Nokton seems like a nice lens but for my future use I'll keep the 40mm on a CL or CLE. I did not see the benefit of trying to use it on an M3. 50mm feels like the right lens on the M3. 

Lens: Voightlander Nokton Classic S.C 40mm f1.4

Film: FomaPan 100