Archived posting to the Leica Users Group, 2002/05/16
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]On Thu, 16 May 2002 14:13:57 -0700 David Young <youngs@islandnet.com> wrote: > The R series cameras (at least the 5,6 & 8) all > list in their instruction books dire warnings > against using two cam lenses. The lenses MUST > have the 3rd cam, or damage can occur! > > Yet these same cameras work with extension > tubes and mirror lenses that have no cams just > fine! (At least, they always have for me!) > > Can anyone here explain WHY this is so? > > What is it about 2 cams that cause problems > with the R series bodies? When on the camera body, the 2nd cam is very close to the 3rd-cam's follower and in some cases the body's cam follower will be pushed by the 2nd cam so that you get reasonably accurate meter readings. The 3rd cam is positioned next to the 2nd cam, and will prevent the cam follower from contacting the 2nd cam. On a no-cam lens, the cam follower doesn't touch anything. I *think* the problem is the different forces produced by the cams. The 2nd cam is supposed to push a Leicaflex (SL or SL2) cam follower along the lens axis, while the 3rd cam rotates the R cam follower around the axis of the lens. The 2nd cam's forces include a small rotational component, so the R body's cam follower will move in response to moving the aperture ring, but the majority of the 2nd cam's forces push the can follower into the camera body. Since the R body's cam follower was designed for rotation movement, not axial, this may eventually damage the cam follower. This is all a guess, since I've never heard of a damaged cam follower caused conclusively by the lack of a 2nd cam. Doug Herr Birdman of Sacramento http://www.wildlightphoto.com - -- To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html