Archived posting to the Leica Users Group, 1998/06/11
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]The Leica RF was designed to focus by matching the movement of a complete 50mm optical unit (ie 5 cm Elmar) as it moved in and out while focusing. Wide angle lenses tend to move less, longer lenses more for the same focusing excursion. SO to couple these to the RF there are essentially two solutions: 1) Differential helix, used in all Leitz/Leica RF coupled non-50mm lenses (except CL lenses) since 1932. 2) Sloped cam, used in 40mm and 90mm CL lenses only. Cheaper solution requiring PRECISE location of camera RF arm. - ---Charles Babington <cbabing3@swbell.net> wrote: > > Paul, > > Thanks for your comments on the rangefinder focusing cam subject. I > guess I misunderstood the original remarks. I see what you mean about > the difference in angle of engagement between my 40mm C lens and my 35 > and 50 Summiluxes. Like you, though, I've never seen any difference in > results on film. > > My reference to "non-rotating" cam was to the arrangement in my 90 > Summicron and 135 Elmarit lenses, where the lens mount simply has a > small plate that engages the wheel on the rangefinder arm. This plate, > which is about a half inch wide and is connected to the focusing threads > that are an inch or two forward of the lens mount, moves only fore and > aft as the lens is focused. There is no rotation to it at all - the > same point on the rangefinder wheel remains in contact with the plate > throughout the focusing range of the lens. > > Cheers, > Kip Babington > _________________________________________________________ DO YOU YAHOO!? Get your free @yahoo.com address at http://mail.yahoo.com