Archived posting to the Leica Users Group, 2005/11/14

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Subject: [Leica] Viewfinders and the 2.5mm
From: red735i at earthlink.net (Frank Filippone)
Date: Mon Nov 14 12:56:55 2005

The movement is totally parallel to the axis of the lens.  The FOV is
therefore displaced by the same amount, relative to the optical axis.
Therefore the displacement or error is 2.5mm in the FOV.

Now I probably need to go look at my Geometry books ( and associated trig
tables) but I would agree with you that to get the 100% correct FOV using
Parallax correction, you would need to adjust something to account for the
2.5mm.  I will accept your 0.14 degrees...

However... being a practical person, 2.5mm is 1/10 of an inch of error in a
FOV that might measure maybe 8x10 inches at closest focus.... so the error
is so small that it account for basically nothing, becasue your FOV in a RF
camera is never 100% anyway...

Go get a SLR if you want 100% framing, and be fussy which one you
choose.....I remember the Nikon F was 100%.  I forget what other had that
degree of accuracy.  Or go cheap... crop.

Chop of the head at 3 feet using this kind of error?  I doubt it.  You might
miss a few hairs.....

Frank Filippone
red735i@earthlink.net


I may have overstated the problem, but I look at it like this:  By my
measurement, there is approximately 59mm between the viewfinder axis and the
lens axis on a IIIf.  Hence, on a IIIf, the VF must be deflected downward by
3.38 degrees, using the paralax adjustment, in order for the VF field of
view to correspond to the lens field of view at 1 meter.  If the VF is
raised another 2.5mm, the VF needs to be deflected downward an additional
0.14 degrees.  Although the change is small, one could chop off the top of
heads because of this when shooting at close distances.
Jim Nichols
Tullahoma, TN USA



Replies: Reply from jhnichols at bellsouth.net (Jim Nichols) ([Leica] Viewfinders and the 2.5mm)
In reply to: Message from jhnichols at bellsouth.net (Jim Nichols) ([Leica] Viewfinders and the 2.5mm)