Archived posting to the Leica Users Group, 2012/10/12

[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]

Subject: [Leica] turn around time for coding lens for digital M's
From: kanner at acm.org (Herbert Kanner)
Date: Fri, 12 Oct 2012 20:00:08 -0700
References: <20599.17411.591734.750669@gargle.gargle.HOWL> <CAJ3Pgh6oy+qWndG1-22sNW3uaKR+jeqs6YO-vmK6+K=nsrRAcQ@mail.gmail.com> <CAE3QcF6q22UgtfbLrejFZa23o1EAshpecaPgg4nbRk0Rj2Jamw@mail.gmail.com> <BAEF0DB452924DFF9966D90D76311564@syneticfeba505> <CAE3QcF6qXRt-ozSbjfhcU1f7c7e3Eh9ko6HymsTP4RKoh4U2bA@mail.gmail.com> <A426AF03412E4FCCA5665ECC12FBBAA0@syneticfeba505> <6262B0B0-77EC-4E8A-A51F-4B55CD534073@acm.org> <CAE3QcF7aXApfNRuYe0H8B-qaP=oSjMis1aTxpJE7P8hVJup1rQ@mail.gmail.com>

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



Replies: Reply from benedenia at gmail.com (Marty Deveney) ([Leica] turn around time for coding lens for digital M's)
In reply to: Message from hartzell at alerce.com (George Hartzell) ([Leica] turn around time for coding lens for digital M's)
Message from roark.paul at gmail.com (Paul Roark) ([Leica] turn around time for coding lens for digital M's)
Message from hopsternew at gmail.com (Geoff Hopkinson) ([Leica] turn around time for coding lens for digital M's)
Message from tedgrant at shaw.ca (tedgrant at shaw.ca) ([Leica] turn around time for coding lens for digital M's)
Message from hopsternew at gmail.com (Geoff Hopkinson) ([Leica] turn around time for coding lens for digital M's)
Message from tedgrant at shaw.ca (tedgrant at shaw.ca) ([Leica] turn around time for coding lens for digital M's)
Message from kanner at acm.org (Herbert Kanner) ([Leica] turn around time for coding lens for digital M's)
Message from hopsternew at gmail.com (Geoff Hopkinson) ([Leica] turn around time for coding lens for digital M's)