Archived posting to the Leica Users Group, 1999/08/30
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Chandos, I had excatly the same problem - and I found exactly the same causes. Don Goldberg fixed the M3 for me at very low cost. I think he increased the spring tension. Interestingly, the problem only occurred on one of my M3's, the others were fine (all were made in 1959) best of available darkness, Alistair - -----Original Message----- From: Chandos Michael Brown [mailto:cmbrow@mail.wm.edu] Sent: Monday, August 30, 1999 11:19 AM To: leica-users@mejac.palo-alto.ca.us Subject: [Leica] More fun w/Noctilux and M3 Following my earlier posting about the "looseness" of the Noctilux on my M3, I spent a pleasant couple of hours fiddling around with both. I offer a few conclusions based on the purely empirical nature of my research. To wit: Both the 50/1 and the 75/1.4 exhibit a similar propensity to uncouple from the M3. Through repeated and accurate testing, I determined that there's enough play in the M3 lens flange locking mechanism to allow for lateral movement of the lens in the mount (rather than the rotating movement that mounts and locks the lens). Often this movement (< .1mm) is sufficient to lift machined notch in the lens flange clear of the locking pin, which in turn, allow a minor rotation to loosen the lens in the mount. For the purposes of experimentation, I adjusted the height of the locking pin by shimming it w/ a bit of film-stock (it's tougher to describe this than to do it). This modification dramatically improves the security of the lens. This accomplished, I thought to examine the degree of wear in the mount be comparing it with an M4P. The 50/1 and 75/1.4 mount securely to the M4P with *no* play whatsoever. What I notice immediately is this: the M4P mount was re-engineered precisely to correct this problem w/ the M3. The M4P beefs up the lug directly beneath the locking pin, in effect, increasing the coupled lug-to-flange surface area of the lens/body mounts, which, in turn, prevents lateral movement in the lens. The M3 relies more than the M4P on the spring tension of the mount to secure the lens. I don't use an M6, but I assume that it incorporates the M4P design or some refinement of it. Preliminary conclusion: while the M3 VF is wonderfully well suited to the Noctilux, I'm not entirely certain that the mount is robust enough safely to accommodate the lens. I'm not going to stop using it, but I offer these observations as a caution . . . Chandos Chandos Michael Brown Assoc. Prof., History and American Studies College of William and Mary http://www.wm.edu/CAS/ASP/faculty/brown