Archived posting to the Leica Users Group, 2012/10/12
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]You have been a great source of information, Geoff. BTW the link you included did not work tonight (7:59 pm PDT) because of "internal server error". I gather from other postings that the two helices that constitute the differential thread can be rotated independently relative to the lens elements. I can see where adjustment would be tricky. Herbert Kanner kanner at acm.org 650-326-8204 Question authority and the authorities will question you. On Oct 12, 2012, at 4:51 PM, Geoff Hopkinson wrote: > More than one log you threw on the fire, Herbert ;-) > Yes there really are lasers and computer analysis involved!. I've watched > the rangefinder adjustment done. Mere mortals don't get invited into their > lens assembly clean rooms though. > > DP Review posted an informative article in 2009 you might like to look at. > http://www.dpreview.com/articles/leicafactory2009/ > Look at the sensor positioning adjustment in the body and the rangefinder > adjustment. > > Digital M's are not only more critical (due to the effectively zero depth > of the sensor) with lens adjustment but people can readily see any (human > or equipment) error at high magnification on their computer monitor > > Cheers, > Geoff > http://www.pbase.com/hoppyman > > > > On 12 October 2012 15:51, Herbert Kanner <kanner at acm.org> wrote: > >> 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 >> >> Question authority and the authorities will question you. >> >> >> >> >> > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information