Archived posting to the Leica Users Group, 2004/10/28

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Subject: [Leica] Infinity and beyond
From: jbcollier at (John Collier)
Date: Thu Oct 28 14:08:56 2004
References: <>

Very, very, very seldom does an M lens turn too far. Very, very, very 
commonly the rangefinder is slightly out such that the superimposed 
images pass each other at infinity.

The very first thing to check is that what the heck you are focusing on 
is far enough away. I recommend 3 kilometers or 2 miles as a minimum. 
Do not try it through glass either as window glass is not very flat.

John Collier

On Oct 28, 2004, at 12:07 PM, Jean Louchet wrote:

> Hi all,
> No, John, what Alexander says means that the RF coupling is just right 
> (he
> gets a clear cut image in the RF patch when the lens is set at 
> infinity or
> close to), what is wrong is where the lens focus ring stops. What he 
> does
> not say is whether his pictures are sharp when he relies on the RF, 
> but it
> seems they are (?)
> If it is so, then adjusting the rangefinder would put it all out of
> adjustment: don't do it!
> Alexander, I'd say that as long as the rangefinder coupling is right, 
> you
> can live with this little problem and your pictures should be sharp.
> Sorting out this problem is tricky, as on most lenses the stop is
> contained in the focus adjustment ring itself, not in the barrel just
> underneath that actually controls the optical block's position. If you 
> are
> already used to take a lens apart and adjust it, you may remove the 
> small
> screws (4 I think) on the focus adjustment ring, pull the focus ring
> out of the lens and check what is wrong with the stops. The difficulty
> there is that if you don't put it back exactly in the same position it 
> was
> before, your lens will have to be completely re-adjusted, which 
> requires a
> couple of special tools. Personnally, I do this sort of things on 
> Soviet
> lenses but I would not take the risc on a summicron.
> First thing to do is check it your images are sharp at full aperture. 
> If
> they are, then I would keep it as is. If not, then a good workshop... 
> but
> the fault is in the lens.
> ------------------------
>> From: John Collier
>> Not an unknown problem and easily fixed in a CLA. I am assuming you
>> have several lenses and only this one goes past infinity. If you only
>> have one lens, one body then just adjust the rangefinder to suit.
>> On Oct 28, 2004, at 12:31 AM, Alexander Glissan wrote:
>>> I have a 1970's 'cron f2 which seems to go to infnity and then a bit
>>> past it. When focussing though I get a clear cut image in the RF 
>>> patch
>>> at or just before infinity and then as I rotate the focus past the
>>> infinity mark, my image goes a little bit out of focuss. Is this a
>>> known personality trait of this lens or does it needs fixing?

Replies: Reply from timatherton at (Tim Atherton) ([Leica] Infinity and beyond)
In reply to: Message from jean.louchet at (Jean Louchet) ([Leica] Infinity and beyond)