The short flange usually means the original focusing mechanism on the lens must be retained, but most of the old rangefinder lenses have very long minimum focus distance of about 0.8-1.0 meters (3 ft). I love to take close up pictures and this is just not very useful for me. What I what is a method that allows me to focus very close, but also be able to attain infinity focus. The answer is a helicoid with large opening, which allows the lens to go inside of the helicoid, and thus get closer to the sensor in order to achieve infinity focus. I found that most of these lenses have a barrel sizes just shy of 58mm, perfect to put a 58mm filter ring on the lens, and then mount the lens on the helicoid.
Rangefinder Lenses: On camera - Nikkor-H 48mm f2, on the right, Minolta Rokkor-PF 45mm f2, Fuji 4.5cm f1.9.
The focus helicoid I bought from the generic junk variant with a 58mm opening, and a 58mm mount. This helicoid has the same sh!t quality as the 17-32mm that I bought a few years ago. When fully extended, there is a lot of play and it feels like it would break apart. The German and Japanese have perfected the helicoid decades ago, and I just fail to see why we still have lousy quality on new helicoids. But, helicoids with large opening is not easy to find and they are usually expensive, because most people would opt for the M42 version. I just have to work with with I have.
So far, I have converted three lenses and they all work beautifully, except the Nikkor-H 48mm f2, which has the aperture stuck at wide open. The Fuji 4.5cm f1.9 and the Minolta Rokkor-PF 45mm f2 both works beautifully. The lens can now focus very close, and yet I can still focus to infinity.
First snow storm in Toronto. Shot through window - Fuji 4.5cm f1.9 & Sony A7.