Archived posting to the Leica Users Group, 2007/04/16

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Subject: [Leica] Fwd: Was: more M8 Noctilux questions, Now DOF
From: faneuil at gmail.com (Eric Korenman)
Date: Mon Apr 16 13:34:20 2007
References: <C248EDC3.10911%robert.rose@mac.com> <82c9dd70704161333l5d69cdbfj1913f18ed54fdc7a@mail.gmail.com>

thanks - I must admit that messing with the innards and having sucess
was enabling.
Of course it could have gone horribly wrong as well..
But nice to know you can do this easy adjustment yourself without a
trip to NJ or Solms.

The M6 does not have an adjustable hex nut in the cam roller.
Does the M7?

Interesting that it isn't really a malalignment issue, just tolerance.
Seems that the added minute thickness of film is more forgiving than
the near perfectly flat film plane of the M8 sensor.

I haven't tested it, but I would assume similar Noctilux shots at
f/1.0 on film and M8 sensor would show differing DOFs. Rough testing
with a ruler shows about 2-3 cm of DOF with the M8.

Eric

On 4/16/07, Robert Rose <robert.rose@mac.com> wrote:
> Eric,
>
> Good for you!  You are now master of your fate, captain of your ship.
>
> BTW, now try your lenses at f/4.  If there is any focus shift, it will
> appear around there.  At smaller f/# the increasing DOF takes care of the
> problem.  So, I either shoot wide open (f/1, f/2 as the case may be) or at
> f/8, where all of my lenses are sharp as a tack.
>
> If you look at the Leica technical papers (or your lens barrel), you will
> notice that most of the DOF is behind the focus point.  Here is a table for
> the Noctilux focus at 5 meters (other 50mm Leica lenses should be similar
> for same f/#).  The distances are in meters.  Notice that at f/8, 3/4 of 
> the
> DOF is behind the focus.  At f/16, a whopping 98% is behind the focus.
>
> f/  Near    Far   DOF    Near % Far %
> 1   4.715   5.322 0.607   47%   53%
> 1.4 4.618   5.451 0.833   46%   54%
> 2   4.472   5.671 1.199   44%   56%
> 2.8 4.291   5.994 1.703   42%   58%
> 4   4.045   6.553 2.508   38%   62%
> 5.6 3.758   7.486 3.728   33%   67%
> 8   3.398   9.523 6.125   26%   74%
> 11  3.035   14.45 11.415  17%   83%
> 16  2.578   107.5 104.922  2%   98%
>
> Bob Rose
>
> ----------------------------------
> Message: 11
> Date: Sun, 15 Apr 2007 15:37:39 -0400
> From: "Eric Korenman" <faneuil@gmail.com>
> Subject: [Leica] Fwd: more M8 Noctilux questions
> To: LUG <lug@leica-users.org>
> Message-ID:
>    <82c9dd70704151237r3bc30249v6af02c0f88cc469c@mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> UPDATE: With a deep breath and as slush fell from the sky (NE weather
> right now), I took a 2mm hex wrench to my M8.
>
> After about 20 minutes of fiddling and 50 or shots of distant street
> signs and close ups of newspaper (!), my Noct appears to focus near
> perfectly. My 35mm and 50mm crons seem to focus just fine as well.
>
> It took the Noct to show me that the M8 was so slightly out of adjustment.
>
> Eric
>
>
>
>
>
>
>

Replies: Reply from jbcollier at shaw.ca (John Collier) ([Leica] Fwd: Was: more M8 Noctilux questions, Now DOF)
In reply to: Message from robert.rose at mac.com (Robert Rose) ([Leica] Was: more M8 Noctilux questions, Now DOF)