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

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Subject: [Leica] Re: Facts revisited
From: Jim Brick <>
Date: Thu, 10 May 2001 09:57:50 -0700
References: <> <>

It seems to me (logically speaking) that if a perfectly focused
(non-defocused) lens registers 100 lp/mm while on a tripod and only 20
lp/mm while hand held - to equal a defocused lens while on a tripod - if
you hand hold the defocused lens (already at 20 lp/mm) you simply
exacerbate the problem to worse performance.

You certainly cannot get "better" performance than you started with. And
you certainly can make it worse.

A camera that is NOT nearly dead-on in focusing on the film plane, is
simply going to, in all cases, give you WORSE performance than a camera the
IS dead-on in focusing on the film plane.

Why did Contax make the vacuum film plate? Why do MF and LF photographers
constantly whine about film flatness?

It is because the depth of focus parameter (where the lens focuses in
relation to the film plane) is extremely critical. There is NO fudge factor

And all of you Leica folks (me too) love to use your lenses wide open. f/2,
f/1.4, and f/1.0 . Without precise focus ON THE FILM PLANE, you will get
crappy photographs.

You can get lucky. You can be off in your focusing and end up with the
subject actually "in focus." But don't rely on luck. Make sure your
equipment is built to do the job the way it is supposed to be done. This is
where heritage and lineage plays an important role. The best fast precision
lenses, on the best precision body. Pieces that actually were made for each
other. An M3 lens works perfectly on an M6. And a new 90 APO/ASPH lens
works perfectly on an M3. Heritage, lineage, history, and dedication is
what makes it happen.

So do you all still think that the flange to film spec, given to Erwin by
Konica, is an error in engineering or done for a reason? Why won't Konica
mate a Leica lens to a Hexar? Why have people attempted to have this done?
I personally think this is a self answering situation.


At 10:07 AM 5/10/01 -0500, wrote:
>So what's wrong with a visual inspection, then?  If you can't see any
>degradation, does it matter if it is present?  From a practical standpoint,
>what's it matter if the theoretical limit is 100 lp/mm for a photographer
>who hand-holds 95% of the time?
>I ask because I seek your expert opinion, Erwin.  I'm genuinely curious.
>Does the defocus problem only really matter if you're using a tripod, slow
>film, and trying to get close to the theoretical maximum?  If hand holding
>already degrades the image, how important does the mismatch between Leica
>lenses and Hexar bodies become?

In reply to: Message from ([Leica] Facts revisited)
Message from ([Leica] Facts revisited)