Amedeo Muscelli
Established
I see.
In a modified Nikon 55/1.2 for Leica M I have made in the past, that modification was needed. I have a device than check at the same time the focus of the lens and measure the relative position than should have the rangefinder cam by mean of a indicator.
In the case of this 55mm lens, the correction was of 0.5mm. The Contax helical used in the lens had a pitch of 4.5mm for a 50mm lens ( I guess than the Sonnar is exactly 50mm ) thus the 55mm lens is 10% more long than 50mm and the helical should have a pitch of 4.95 being the 0.5mm the correct correction with a error marging of 0.05mm.
I think than the cut of 0.1mm is logic for to reduce focusing problems, I would know the opinion of users of my adapters about this theme, may be I must make them already corrected.
Regards,
Amedeo.
In a modified Nikon 55/1.2 for Leica M I have made in the past, that modification was needed. I have a device than check at the same time the focus of the lens and measure the relative position than should have the rangefinder cam by mean of a indicator.
In the case of this 55mm lens, the correction was of 0.5mm. The Contax helical used in the lens had a pitch of 4.5mm for a 50mm lens ( I guess than the Sonnar is exactly 50mm ) thus the 55mm lens is 10% more long than 50mm and the helical should have a pitch of 4.95 being the 0.5mm the correct correction with a error marging of 0.05mm.
I think than the cut of 0.1mm is logic for to reduce focusing problems, I would know the opinion of users of my adapters about this theme, may be I must make them already corrected.
Regards,
Amedeo.
Roland put a cut into the RF cam of his adapter to translate the motion of the 52.4mm focal length of the Contax to the motion expected by the RF pickup of the Leica. Basically, it looks like the cut-cam on the M-Mount Summicrons to correct for slight deviations in the focal length. The motion of the Contax Helical "overdrives" the RF pickup without this cut.
I'll get some close-ups of the cut, again it is very shallow.
Took some, posted here:
http://ziforums.com/album.php?albumid=176