Archived posting to the Leica Users Group, 2013/01/06

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Subject: [Leica] IMG: Pt.Lobos Formations
From: red735i at verizon.net (Frank Filippone)
Date: Sun, 06 Jan 2013 15:50:03 -0800
References: <CAAsXt4Ou+dC10_6A2vVH0BcG0SKEgCTNL+3wU5K7X6sirhsi6g@mail.gmail.com> <CD0F3685.3090%mark@rabinergroup.com> <CAAsXt4OgVth5zZmwX2o+2jWODs4TTjy2ySmT2yU_M26rCUQ07A@mail.gmail.com> <045f01cdec5f$d2c1fff0$7845ffd0$@verizon.net> <CAAsXt4MqE-+GUc+XjQ3658OLDO=3F2qQJb8sD7oVXn6Bpgw67g@mail.gmail.com>

NOW I understand....

Frank Filippone
Red735i at verizon.net

-----Original Message-----
From: lug-bounces+red735i=verizon.net at leica-users.org
[mailto:lug-bounces+red735i=verizon.net at leica-users.org] On Behalf Of 
Robert
Adler
Sent: Sunday, January 06, 2013 3:32 PM
To: Leica Users Group
Subject: Re: [Leica] IMG: Pt.Lobos Formations

Hi Frank,
Alpa supplies the shims with the mount for the back. They make mounts that
work with HV, H, Mamiya, Pentax, and other cameras. Shims supplied with
each.

There is a YouTube that shows you how to calibrate your MF back to the Alpa
body:
http://www.youtube.com/watch?v=ajteLwe-ntE
It's a two parter...

Basically you take a non-wide angle lens (I use the 80mm), fully open it up
and put the len's at it's infinity focus position. Then, on a clear day, you
shoot something at least 2km away with some detail. Then you move the focus
just a titch closer than the infinity mark (which moves the lens element
further from the back) and compare that to the first image. If the stuff at
infinity is crisper in the second shot than the first, you begin adding
shims in .01mm increments. If it's not crisper you take out shims in .01mm
increments. At some point in the process, the difference in clarity is
undeniable and deteriorates with the addition or subtraction of just 1x.01mm
shim.

So you need your computer when you do this to read and display the files.
It's a back of the car or an on top of a building thing. Once done, however,
you're done. With Alpa you only need to do this once and it works for all
lenses. With other tech cams (e.g. Cambo) the process is different; usually
each lens has to be calibrated and the focus ring change...
Bob

On Sun, Jan 6, 2013 at 2:47 PM, Frank Filippone <red735i at verizon.net> 
wrote:

> That is fascinating.....!
>
> I always suspected it was not as easy as taking out of the box and 
> shooting.......
>
> So how did you get the shims?  And did you do the "calibration" yourself?
>
> Frank Filippone
> Red735i at verizon.net
>
> I found the GG not to be reliable on these technical cameras with 
> medium format backs. I had been using the ground glass, which, though 
> it looked sharp, often was not. These sensor are so remarkably flat 
> that even being off 1/100mm will cause out of focus images. That's why 
> Alpa allows users to shim the piece that holds the digital back onto 
> their cameras to be adjusted with shims by 1/100mm. Other digital 
> technical cameras allow you to adjust the focus point of each lens to 
> the back. The manufacturing tolerance of the back's mounting plates 
> are not within this range.
>
> The difference between my traded in back and this back was .1mm (the 
> back had to be positioned .1mm closer).
>
>
>
> _______________________________________________
> Leica Users Group.
> See http://leica-users.org/mailman/listinfo/lug for more information
>



--
Bob Adler

_______________________________________________
Leica Users Group.
See http://leica-users.org/mailman/listinfo/lug for more information



In reply to: Message from rgacpa at gmail.com (Robert Adler) ([Leica] IMG: Pt.Lobos Formations)
Message from mark at rabinergroup.com (Mark Rabiner) ([Leica] IMG: Pt.Lobos Formations)
Message from rgacpa at gmail.com (Robert Adler) ([Leica] IMG: Pt.Lobos Formations)
Message from red735i at verizon.net (Frank Filippone) ([Leica] IMG: Pt.Lobos Formations)
Message from rgacpa at gmail.com (Robert Adler) ([Leica] IMG: Pt.Lobos Formations)