Archived posting to the Leica Users Group, 2012/10/12
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]It's not that you are wrong, but consider tolerances..... A semiconductor has basically no tolerance in the film plane. It is a few microns thick. Film has the tolerance of the thickness of the emulsion, plus the tolerance of the actual film plane setting device ( rails and pressure plate) and the tolerance of the film backing. So digi-cams are a bit more "fussy" to set up to focusing accuracy...... especially if you have a lens that has almost zero depth of field. It is all about the tolerances.....and how you get there..... Thank you for speaking of how the lenses worked. I wondered a lot about how DAG changed the focus location on my 75. I still wonder. I was told years ago that it is done with spacers.....but DAG did my lens in like a few minutes... which indicates it was not a matter of changing shims. It must be a set screw allowing a helix to be rotated. Loosen the set screw, adjust, tighten the se screw. But I looked and could not find the setscrew... any ideas where it is on a lens? Frank Filippone Red735i at earthlink.net I'm gonna add some fuel to this fire. Maybe there is some technical witchcraft going on that I don't understand, or maybe some of you guys are just plain superstitious and Leica is talking a lot of impressive bullshit about lasers and suchlike. So here is the understanding I've had for years as to how Leica worked interchangeable lenses with a rangefinder mechanism. 1. The rangefinder was designed to work with a 50mm lens in that the as the lens unit moved to and from the film plane, the real end of the lens container pressed against a roller on a lever that actuated the rangefinder mechanism. Other lenses used a pair of threads (the technical term being differential threads) so that as the lens focussed (with greater motions if the focal length was more than 50mm and lesser motion if less than 50mm) the rear cylinder would move the same distance as that of a 50mm lens. With that kind of system, the only adjustment that would be possible would be setting the infinity stop and setting the distance marking ring to agree. Also, there is absolutely no reason for a digital camera to have any different focussing problems than a film camera. It just that the focus might be a bit more accurate since the sensor is rigid and there is always the possibility, despite a pressure plate, that the film is not exactly in a plane. Herbert Kanner kanner at acm.org 650-326-8204