Archived posting to the Leica Users Group, 2001/06/28

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Subject: Re: focus stiffness (was [Leica] Black Hole?)
From: SthRosner@aol.com
Date: Thu, 28 Jun 2001 08:47:16 EDT

In a message dated 6/28/01 3:01:57 AM Eastern Daylight Time, 
mxsmanic@hotmail.com writes:

<< In absolute terms, it is about 1/26 of a stop, so it's not very much, but 
still
 more than many other lenses.>>

I may have misunderstood. When someone says there's play or slack, I assume 
that means the aperture ring moves without affecting the diaphragm.
  
 <<But the lens still has to be disassembled, doesn't it?>>

Not necessarily. And even if there needs to be some disassembly, the lens 
cell itself may be able to be left intact, i.e. the problem may be 
correctible without touching any lens elements or their mounts.   
 
 <<It's like an acoustic piano:  Whenever you tune it, the tuning pins loosen 
a
 little bit.  No matter how careful you are, no matter how good you are, you
 can't avoid damaging (wearing) the pins and their block down a bit with every
 tuning.  And with a lens, every time you undo a screw or force a ring off a
 pressure mount or whatever, something wears down a bit, and it will never be
 quite the same again.>>

I studied piano for most of my youth. There is a great deal of torque applied 
to piano pins and so it is technically true that each time you tune a piano, 
there is some wear on the pin. It is however infinitesmal and requires a 
great deal of fiddling (forgive the pun) with the pins to have any effect at 
all. So you are technically correct in saying that there's some wear, but in 
the real world, fuhgetaboutit. It's a bit like saying that there's some wear 
each time you press the shutter release. True, but so what?

In any event, with lenses there is no equivalent torque, tension or pressure 
on screws or retaining rings. What little resistance or load is required to 
maintain an apereture ring in its click-stop or return an SLR diaphragm to 
its full-open position is supplied by springs or clips whose force is 
carefully calculated to supply only the tension needed for the job. 

I've been photographing with Leica equipment for over 50 years. In that time, 
I've needed very little servicing but that which I've had, returned my 
equipment to me in like-new mechanical and optical condition; and I mean 
like-new. Properly used and cared for, your Leica camera(s) and lenses will 
be usable by your grandchildren 
and, if you're as old as I am, by your great grandchildren. What's the number 
again? Leica shutters are crafted to be able to be used through 400,000 
cycles before requiring service? Some incredible number.
 
It seems to me that you may be overly worried about a problem that doesn't 
exist. Again, as Ted says, go forth and take pictures. 
 
Where in Europe?           Best,         Seth        LaK 9 

Replies: Reply from "Mxsmanic" <mxsmanic@hotmail.com> (Re: focus stiffness (was [Leica] Black Hole?))
Reply from "Ted Grant" <tedgrant@home.com> ([Leica] WAS: focus stiffness- Black Hole?)NOW: Anthony! ;-()