[tech-3d] terms & correct field curvature

[John Toeppen <toeppen@xxxxxxxx>]

Consistent terms are desirable for effective communication. I actually
applaud and am not appalled by Abram, ISU, and those who seek to derive
meaning from words.  Derivation of terms - prior usage of words, can be
revealing.  The word "ortho" means right or perpendicular.  What is
right is situation dependent.  Map making and stereo imagery use similar
methods to achieve different goals. The correct thing to do depends on
the desired results.

Stereo images shot with long lenses have "flattened" fields. (ortho in
the map making sense) This property is desirable if one wants to splice
images to produce a panorama.  If the curvature of field is not
considered, vertical and horizontal offsets are created.  Image
disparities not caused by parallax are distracting and degrade good
stereo.  Thus, one shoots with a "normal" lens to acquire pans. 
Software can correct for some curvature, but it seems best to start with
the right images in the first place.

There is a simple way to produce the effect of a stereo panorama on a
PC. Convert a high resolution image pair into a large interlaced image
(2400 x 3600+). View at actual size using shuttered glasses while using
the arrow keys or scroll bar to scan across the image.  Anaglyph images
can be zoomed into and panned across as well.  One learns that local
misalignments can be due to mismatched curvature of field.  So tell me,
what is the right thing to do?

John Toeppen 
http://members.home.com/holographics

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