Re: [photo-3d] Re: Gary's stereo windows

["John A. Rupkalvis" <stereoscope@xxxxxxxxxxxxx>]

----- Original Message -----
From: "Allan Griffin" <agriffin@xxxxxxxxxx>
To: "photo-3d" <photo-3d@xxxxxxxxxxxxxxx>
Sent: Monday, February 26, 2001 6:25 PM
Subject: [photo-3d] Re: Gary's stereo windows

Some thoughts in general about all of the comments so far.  I wonder if the
term "stereo window" in itself might be misleading or confusing to some
people.  It invites comparison to a real window, and the comparison is not
entirely valid.

Picture elements that lie beyond the stereo window do indeed behave like
they do with a real window, where objects on the other side of the window
are occluded by the window frame both in a stereo image and in real life.
So far, so good.

In real life, however, objects closer to you than the real window are not
occluded.  You can see them whether they are within the frame of the window,
or outside of its boundries.

With a stereo image, such objects are occluded by the frame edge, whether
they are beyond the frame or in front of the frame.

To avoid such unnatural partial occlusion, it is necessary that closer
objects not touch the frame.  And therein lies a problem.  The closer they
are to the camera, the smaller these objects must be to avoid intersecting
with the frame edges.  It is this concept that many people seem to have
trouble with.  They compose the image so that the closer elements do not
touch the edge.  Then thinking of the stereo window as a constant, they move
the camera or the subject closer.  Now the frame edge occludes the closer
element(s).

Teaching the concept of the stereo pyramid makes the concept of the stereo
window much easier to understand.  And, the term "stereo pyramid" does not
convey a mental image of something that is quite different from what the
term would connote in real life.

JR


 

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