Windows for Smarties I...

[P3D <LeRoyDDD@xxxxxxx>]

...well the other title is copyrighted, no doubt. :=)

Orthodox window rule:
Mount the main subject at the window...
     except if there's a closer object "touching/breaking" the window
     except if the main and other subjects are far away
     except if it's close and infinity(very far) points are included

     Wait a minute! Where do we get this "window"... at the Home Supply
store? :=)

     There's a window that comes with every set of images from a properly
designed stereo camera.
     The lenses aren't centered on the film apertures, but are shifted
slightly inward. This lens shift creates one distance at which both lenses
place the same visual field in the film apertures, which would not happen
with parallel lens axes. It also shifts infinity points outward on the film
relative to the film apertures.
     If you design your viewing system to "see" the infinity points parallel,
the unmasked image edges will be at the camera window distance and form the
"window." Objects farther than this will be behind the window; objects closer
will be in front of the window.
     As I recall, the Kodak window is at about five feet and the Realist at
about seven.

     But, of course, most cameras have tight image spacing... some even
overlap slightly... and image apertures can be irregular... so when we mount
our film, we mask the images down.
     A mask/mount which replicates the camera spacing of the image apertures,
with its apertures just equally reduced in size will replicate the camera
window for images placed in it at camera spacing. This is "normal" mounting.
The mask and an object at the camera window distance will be in the same
plane and an infinity object will be viewed with parallel "vergence."
     Relative to this "normal" mask, you can move the scene forward or back.
The window is now a compositional device. Many feel that having the closest
subject at the window is more esthetically pleasing. They would push the film
chips together and bring an object at 12 feet up to the window. If an object
is in front of the window and touches it, say a tree branch, many would feel
uncomfortable with it seeming to "hang in mid-air" cut off in front of the
window and move the film chips out to push the branch to just behind the
window.

     If you move your scene so as to depart from the "normal" too much you
can have some problems.
     A regular stereo shot of far mountains with nothing closeup(you wouldn't
take one like that, would you? :=)) isn't improved by bringing the mountains
forward. Using the window to establish "nearness" and allowing the mountains
to appear in all their non-stereo glory at infinity is probably a better
choice.
     A regular stereo closeup at four feet with infinity in the scene, if
pushed back to a "normal" window will cause divergence of the eyes viewing
the infinity point, perhaps painfully. This view needs to have infinity
removed from the scene(quick find the wayback machine!) or be mounted by the
"double depth" method of moving the window forward, rather than moving the
scene back.

Moderation in all things.(Except *harmless* :=) pleasures?)

     Corrections, additional thinking, other viewpoints welcome...

    More to come...

LeRoy Barco
LeRoyDDD@xxxxxxx


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