P3D Re: Alignment of seperate 35mm Cameras...

["Dr. George A. Themelis" <DrT-3d@xxxxxxxxxxxxxxxxxxxxxxxxxxx>]

>       O.K.... So I'll return to Parallel shooting, but I think
>    what I observe may be happening is that when shooting 
>    parallel axis, that the stereo window is PARALEL to each
>    camera's film plane.  But when the camera is adjusted to
>    where the effect is Converging at some point before
>    infinity,  it appears that the two seperate lenses see the
>    exact point of convergence, but that the stereo window is 
>    only the same at this point. 

Hmmm?  :-)

The stereo window is 3-dimensional concept.  Each single picture
has a "window" of its own.  This can be the black border or the
edges of the picture.  When two pictures are combined to form
a stereo picture, then the edges are also combined to form a
3-dimensional "window" that frames the picture.  Perhaps your
problem with converging axes is that we call "keystone distortion".
As you go away from the center of the frames there are vertical
displacements that make viewing difficult.

>    <<<There are many good books out there, explaining the
>    <<< concept.  I liked  the "3L" rule that says:  "The Left
>    <<< eye sees Less in the Left side"
>    
>       -Would you mind going into a little more detail on
>     the above? I do not use a "mask", but instead use a 
>    hooded viewer without the long focusing bar (I cut it off)
>    and just move the picture until they appear to be at the
>    optimum position for cropping/mounting. (as opposed to
>    just cutting an exact amount off of each image with 
>    something like a mask)

I recommend reading Jac. G. Ferwerda's "The World of 3-D - A Practical 
Guide to Stereo Photography".  Joel Alpers of "Rocky Mountain Memories"  
carries copies of this book for sale in the USA.  (Also, I believe, 3-D 
Book Productions in the Netherlands)

The hooded viewer complicates things because it arbitarily crops
the pictures.  This is especially true for the Keystone Telebinocular
which has a small opening and creates a stereo window of its own,
interferring with the built-in stereo window of the pair.  (This
situation is similar to viewing 7p slides in a 5p viewer - the
viewer crops the picture setting a window on its own which might
not be the window that makes whanted to have.)

You said you do not use a mask.  Still, the edges of your pictures
define a stereo window.  You can control this window by cropping the
pictures appropriately.  Try removing the metal plate in front of
the lens assembly in your Keystone Telebinocular (I have done this
in mine).  Then you can see what stereo window you have set in your
pairs.

Best regards -- George Themelis


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End of PHOTO-3D Digest 2773
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