Archived posting to the Leica Users Group, 1998/04/15

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Subject: Re: [Leica] focus at infinity
From: "Harold Gess" <gess@icon.co.za>
Date: Wed, 15 Apr 1998 22:43:40 +0200

Hi Luggers

After reading all the posts on this subject I decided to try an experiment
and it worked rather well so I thought I would share it with the Lug.

I took the back doors off my various Leica M's and mounted them on a tripod,
took the plain ground glass from one of my Nikon F2's and placed it resting
on the film rails of each of the M's. I focused each of my lenses on a
target fairly close by and then observed the ground glass with a loupe.

There is indeed some variation among the lenses when observing through the
viewfinder (they don't all find infinity at the same point), and there is
some variation depending on combination of body/lens. on the groundglass the
focus of some lenses (in particular my 50mm Summicron Canada) is not quite
on the spot when compared to the viewfinder, but I think the difference is
actually negligible (say  focus at closest focus is out by maybe 1- 1.5 cm.
I guess on a F2.0 lens that would be considered within acceptable tolerances
(I'm not sure)?!

On the Noctilux focus seemed to be spot on on all bodies. So did focus on
the 35mm Asph. Summilux. This is strange as the 90mm Summicron seemed happy
on two bodies and fractionally out on the third. Strange!

Rock photographer Jim Marshall who shoots with M4's (he apparently has 5 or
6 of them) apparently has his lenses individually adjusted to individual
bodies and then never takes them off!! He reckons it's the best way to get
supreme accuracy!!!

Hope this is of some interest

Harold
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