P3D Re: Zero Magnification?

[Bruce Springsteen <bsspringsteen@xxxxxxxxx>]

Another way to ask George's question may be: "What is the distance
travelled by the image in a View Magic viewer (on its periscopic path)
that should be added to your eyes' distance from the print, to obtain a
total viewing distance from which you can determine magnification?"  Any
total over 250mm will be negative magnification, closer distances will
require the addition of lenses to the system (not a bad trick with +3
reading glasses, I've found).  There is no standard viewing distance
established in this format that I know of.

Of course you will also have to determine how much enlarged the print is
from the negative, and know the focal length of your shooting lens, if you
want to make an evaluation of your "ortho status" when viewing with the
ViewMagic.  This must also be done to determine orthostereo in other print
viewing systems.  My Holmes viewer gives me "ortho" when a print four
times the negative size is matched by a camera focal length of about 45mm,
one quarter of the approximate 180mm lenses of my antique viewer.  Lots of
room for "fudge" there.

Bruce


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