[Leica] Re: Leica Users digest V19 #27

["Randy Andrade" <smaugmra@abq.com>]

Doug, I wish you would post some jpg's!  Perhaps they could be uploaded to
the Group's homepage and added to the FAQ, as I'm sure I'm not the only
dunderhead who asks such elemntary questions.  Heck, this whole thread
should go into the FAQ!In all probability, this may be a confusing point for
many newbies (though I've been using an M3 since 1958, and an SL since the
70's...it's just these newfangled R-#thingamigingies that have me
confused!).
Randy

Doug Herr wrote:

> There are 2 ramped cams.  The first one, originally for the Leicaflex
Standard, is at the top position on the lens mount.  Cam #2 is a similar
ramped cam at the bottom of the lens mount.  This was for the Leicaflex SL
and SL2.  The 3rd cam is the stepped thing next to #2.  I have seen one lens
(21mm Super-Angulon-R f/4.0) where the 2nd and 3rd cams are made from a
single piece of metal; in all other lenses I've seen they're two pieces.  I
gotta post some jpgs of the cams some day, with circles and arrows and a
paragraph on the back describing each one...
>
> Doug Herr
> Birdman of Sacramento
> http://ourworld.compuserve.com/homepages/telyt
>

The 3rd cam isn't as long as you've described it.  Yes, it's located inboard
or radially closer to the center or  axis of the lens but it's not any
longer than the 2nd cam.  With the lens off the camera body, move the
aperture control ring and you should see all 3 cams moving in synchrony (as
well as the aperture control lever).  If the thing you're looking at doesn't
move with the slopey cams, then it's not the 3rd cam.

All the cams do is tell the camera body's meter what aperture the lens will
be at when it's stopped down to working aperture.  In the case of the 1st
cam, it tells the camera what the actual aperture is (for the Leicaflex
Standard's external meter).  The 2nd and 3rd cams tell the camera what the
working aperture is relative to full aperture, i.e., how many stops the
working aperture is smaller than full aperture.  This is what the TTL meters
of Leicaflex SL and all subsequent R-cameras need to know.

It may seem silly to have both the 2nd and 3rd cams doing the same thing but
it can be explained with a review of the R-cameras' history: when the
Leicaflex was developed, Leitz used the same technology for transferring
aperture info (the 1st cam) as they had used for transferring focus distance
to the LTM and M cameras.  The SL's 2nd cam merely followed in this
tradition, and likewise, the SL2 used both the 1st and 2nd cams, the 1st for
its viewfinder aperture display, and the 2nd cam for metering.  The SL2 was
built in the mid-1970s when Leitz was in financial trouble, the SL2, seen by
the public as obsolescent technology, was losing money for the company, and
the company had little funds for R&D.  A few years before, Leitz and Minolta
entered a technology-sharing agreement, and some of the earliest results of
the technology sharing appeared in the SL2 in the form of a re-pivoted
mirror which allowed lenses with Minolta's back-focus specifications (the
distance between the r!
ear element and the film plane) to be used.  Along with this change, some
Minolta-built lenses became available in an SL2 mount: 16mm Fisheye, 24mm
Elmarit-R, and the early 80-200 f/4.5 zoom (don't confuse this zoom with the
current 80-200 f/4.0).

A further development of the Minolta agreement was the R3 camera body of
1976(?) which was derived from a Minolta body.  The Minolta camera used a
meter coupling very different form the Leicaflex meter coupling.  I don't
know if this forced Leitz to change to the R-style stepped cam, but the
R-cam (a.k.a. 3rd cam) is much easier to work with than the Leicaflex cams
when designing and using extension tubes and teleconverters.

The 3rd cam can be added to 1-cam or 2-cam lenses, and if you have any of
the R-only lenses that have only the 3rd cam, usually the Leicaflex metering
cams can be added.  ROM lenses replace the Leicaflex metering cams with
electronic contacts.  These lenses cannot be used on Leicaflex bodies, but
for a price many can be converted to 3-cam lenses.

Doug Herr
Birdman of Sacramento
http://ourworld.compuserve.com/homepages/telyt

>
> Neat.  So if I want to replace a ROM implant with a third cam,
> can I buy a bag of parts and do the surgery myself?
>
> Or are there complex and fiddly calibrations that need to
> be done?
>
> Thanks
> Vick
>

ROM lenses also have the 3rd cam.  The ROM contacts are in the position the
1st cam used to occupy, and would be damaged by the cam follower on
Leicaflex Standard and SL2 bodies, so ROM lenses have an R-only mount.

My understanding is that the ROM stuff can be replaced with Leicaflex cams,
and the R-only mount can be replaced with the Leicaflex mount (which is what
I did with my 14256).  There are probably some shims involved in getting the
1st and 2nd cams in the right position; some R-only lenses may have the
mounting holes already drilled in the inner aperture control ring (my 50mm
Summicron-R did) but others may not.  It's a fiddly conversion and
itty-bitty parts can get lost or go "sproing" if you're not careful.