Archived posting to the Leica Users Group, 2001/05/10

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Subject: Re: [Leica] Facts revisited
From: Dante Stella <dante@umich.edu>
Date: Thu, 10 May 2001 18:16:29 -0400 (EDT)

> The Konica facts have as source the Konica Headquarters Europe, in Germany. I 
> spoke to the service people there, who reproduced wordly (from the English 
> specification details) that the film register is 28.00mm plus/minus 0.03.

So relative to the Leica specs, that is Leica -0.01/+0.05mm?  That;s not
what you seemed to say yesterday when it was 28.00mm +/- 0.06mm.
Forget that I have any advanced mathematics behind me, but doesn't that
make it more likely to have the backfocus longer than shorter?  I would
assume that it is much more disastrous to have a backfocus too short,
since that puts the plane of focus beyond infinity (and indeed the
focused image behind the film).  If given a choice, I think I would rather
have a slightly longer BF distance than shorter one, since having it
longer maximizes your depth of field.

> He also noted that it is impossible for any company with engineering quality 
> status as Konica or name anyone else, to depart from that figure significantly.

What figure?  The measurement or the tolerance?  Is he saying that Leica
can't do it either?

> He said that it is possible to match a Konica body to Leica lenses, BUT then 
> you need to adjust the Rangefinder mechanism too. It is not enough to change 
> the boyonet, if that could be done. 

> He admitted that sometimes a user with a Konica body does not have problems 
> when using leica lenses but that it not generally the case.

Most of the time, maybe all of the time.  I have heard of only one person
having a the camera focus short.  Everyone else has complained about
near-limit focus with the Summilux.  That is enough to put an M6 in
failure moder, and when the DOF is razor thin, does not give a reliable
result on any camera.

> I know of Hexar RF bodies that depart from the quoted specs. I do not know why 
> that happens or whether these bodies have been adjusted individually.
> I do know that I do not trust the wellknown visiual inspection method: I shot 
> pictures with a Hexar/Leica combo and see no problems. 

So all of these comments are based on what someone told you rather than
the "as-built" measurements and empirical testing of entire systems?  It
sounds a lot like poisoning the well to me.

> that a defocus of 0.2mm will reduce the definition and contrast of a lens in 
> the same proportion as handheld shooting can do.

So Leicas can degrade the performance, too.  0.2mm is FOUR TIMES the
maximum deviation from Leica specs and TEN TIMES the nominal difference
between the KM mount distance and the M mount.

> To be precise: if the optimum quality of a lens is 100 lp/mm, then a handheld 
> shooting can reduce it to 20 lp/mm with low contrast. A defocus by .2mm will 
> also reduce the optimum to 20 lp/mm. This being the case, any test with 
> handheld shooting will mask the defocus reduction.

What's the defocus with handheld shooting?  Is it an average?