Archived posting to the Leica Users Group, 1996/12/07

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Subject: Re: Mysterious pins on R8 lensmount
From: "Stefan Kahlert" <uzs13b@ibm.rhrz.uni-bonn.de>
Date: Sat, 7 Dec 1996 10:55:19 +0000

> I would add that the feel of the focusing ring changes when AF is added.  My
> theory is that to allow the AF motor to work while minimizing power and size
> requirements, the focus mechanism of the lens needs to be easily moved. Much
> more easily than a typical MF lens.  When you manually focus an AF lens you
> get a real sloppy feel to the focus.  This also means the lens focus will
> change at the slightest bump.  

Some but not many AF-lenses give the proof, that it ain't 
necessaribly so. My Nikon 180/2.8 AF couples to a smooth resistance-
element and some other lenses from other manufaturers do so too.
The lens feels better (at least for me) than it's MF predecessor
which lacks IF. Even the Nikon 300/2.8 *MF* has a resistance-element
that can be uncoupled to focus it with your little fingers tip
(If you like to). So there can be loose focussing also in decent MF 
lenses.

I don't think that smooth MF-focussing and AF-capability in one lense 
is a contradiction. AF lenses can be nice as MF-lenses too.
But obviously this counts only for expensive lenses, 
not for standard-zooms or cheap fixed-focal length lenses or macros
where the short focussing-angle easily becomes a problem near 
infinity.
At the Leica price-level it probably wouldn't be that much of a 
problem to integrate the best of both worlds into a lense.

But it would be a big investment for Leica to develop a full new line 
of lenses (mechanically new) that most likely isn't justified by
it's small market share. 
Look what Yashica did with the Contax AX.

best wishes

Stefan

 
- --
Stefan Kahlert, 
Medizinische Poliklnik der Universitaet Bonn
uzs13b@uni-bonn.de