Re: [photo-3d] Re: Getting closer with mirrors

[Brian Reynolds <reynolds@xxxxxxxxx>]

Peter Davis wrote:
> Jim Harp wrote:
> >I haven't had a chance to get a decent stereo pair of the setup, so I
> >put the rig on my scanner - here it is:
> >
> >http://www.egroups.com/files/photo-3d/Twin+SLR+%22mirror%22+close-
> >ups/Twin+mirror+rig.jpg>
> >
> >I should have mentioned that the shots I posted are mounted for
> >cross-eyed viewing - if you change the file suffixes to "jps" they
> >should be viewable in Depthcharge.  I had a question off-list about
> >varying the lens seperation with this rig.  I'm thinking of
> >building two bars, one with the mirrors set as close as possible
> >(as shown above) and one that would emulate the RBT S-1 spacing by
> >separating the mirrors by about 1 1/2".
>
> This seems like such a cool idea, but don't the mirrors introduce
> keystone distortion?
> 

So long as the vertical axis of the mirrors remains parallel with the
vertical axis of the camera backs I don't see how keystoning would be
introduced.

By the way, I have some ideas for making a rig that would allow you to
varying the lens spacing at will (within limits).  You could make a
bar shaped like a T.  One camera rides on each arm at the top of the
T.  The mirrors are mounted on a block on the stem of the T.  After
adjusting the camera separation you slide the mirror block in and out
until you get the optical axis separation you want, and verify through
the camera viewfinders that the mirrors cover the field of view.  I
may have seen this in a book somewhere (which would explain why it's
such a good idea :).  Various threaded rod mechanisms could be
devised to ensure that the cameras are spaced equally on either side
of the centerline.

-- 
Brian Reynolds                  | "Dee Dee!  Don't touch that button!"
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http://www.panix.com/~reynolds  |    -- Dexter and Dee Dee
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