P3D Homemade splitter / 1/30 rule

[boris@xxxxxxxxxxxx (Boris Starosta)]

The 1/30 rule is a pet peeve of mine.

>From: "Jeff Toman" <jtoman@xxxxxxxxxxxxxxxx>
...
>splitter is hyperstereo, with a base of 112mm.  Using my 50mm focal length
>lens, my near subject must be several feet away (approx. 11) by the 1 in 30
>rule.  Nevertheless, the composition is not a problem.

Jeff: the 1/30 rule limits "on film deviation" and is intended to insure
that there is not too much parallax in a view, expecially when projected.
The 1/30 rule is also a simplification, as it assumes that you are
including infinity in the view.  So the rule is to limit the maximum on
film deviation of two homologous points at infinity.

This is important when you project images onto a large screen, where
ideally you do not want the maximum to exceed 2.5 inches.  But "ideally" is
just that.  More separation of homologous points is possible on screen for
many viewers.

If, however you are producing stereo cards, to be viewed in a stereoscope,
the maximum is not quite so important (though not unimportant).

Why do I say all this?  I have seen more shots ruined by the 1/30 rule than
I care to remember.  In folios, exhibitions, on the web... I see either
subjects photographed from too far away, or I see nearby subjects
photographed with an insufficient stereobase - with the authors pointing
out that they adhered to the rule.

If you can limit depth in your scene (crude example: shooting a head &
shoulders portrait in front of a wall), you can get away with much more
stereobase - or you can get a lot closer than the rule indicates.

With a 112mm stereobase, shooting a "shallow" subject, you can probably get
as close as four or five feet.  The result: you will get a much better
stereo effect.

But your splitter may have to be able to "toe-in."

Boris

Sometimes, good candid shots require careful posing.
        - Roy Hensel, SSA 2x2 folio.

Boris Starosta            boris@xxxxxxxxxxxx
                          http://www.starosta.com
usa 804 979 3930          http://www.starosta.com/3dshowcase