Re: Medium format 3d

[P3D Greg Erker <erker@xxxxxxxxxxxxxx>]

>How well would it work if I made a medium format camera with two
>80 year old B&L Rapid Rectilinear lenses with a focal length of 150mm?

  The "normal" lens for a 6x6 camera is 75 or 80 mm focal length
so you would be shooting with about double that. This means that
the angle of view of the camera is about half that of one with
a normal lens.  This is similar to shooting with a Realist format
camera with 70 mm lenses.


>I would use this to make B&W prints for a holmes stereoscope.  What
>spacing would be the best or most useful?  Should I make it 2 1/2
>inches to match peoples eyes, or 3 1/2 to match the viewer?

  If you make contact prints (ie same size as neg) then you
should view with lenses of the same FL to avoid stretch or
squish.  Thus 150 mm FL would be best. Longer focal lenghts will
give stretch.  A 200 mm FL viewing lens would give you a
33% stretch.  For comparison, the Realist Red Button lenses
are 44-ish mm FL vs the 35 mm FL of the camera. So there is
about 26% stretch when viewing with this system.

  One nice thing about MF stereo is that it is fairly easy
to get lenses that match the FL of the camera and that have
enough coverage to allow you to see the whole image.  They aren't
cheap, but 80 mm FL range achromats in 30-40mm diameter are
available from Edmund Scientific.

  The spacing of the lenses in your camera (or shift between
shots with a single camera) should match your eye spacing.
If you use a larger spacing everything will look smaller
(proportionally) in all 3 dimensions.

  The 3.5" spacing of the stereoscope prints is taken care
of by the prism in the viewing lenses.

Hope this helps - Greg E.



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