Archived posting to the Leica Users Group, 2012/10/12
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]And the position of several of the internal elements / groups can be adjusted. And the FLE lenses have 4 helices. Marty On Sat, Oct 13, 2012 at 1:30 PM, Herbert Kanner <kanner at acm.org> wrote: > 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 > > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information