Re: [photo-3d] The jig's up (part II)

["Dr. George A. Themelis" <drt-3d@xxxxxxx>]

From: "Dr. George A. Themelis" <drt-3d@xxxxxxx>

A common misconception:

If you tilt the camera, the chips will not be "out of
alignment".  The chips will be perfectly aligned but
the scene will appear tilted which is disturbing for
psychological (spelled right this time?) and not
technical reasons.  At an extreme, you can tilt
the camera 90 degrees sideways for special effects
(just ask Jon Golden!)

I am sure Ken is aware of this, but if you attempt to
rotate the chips to remove this tilt, then you will
introduce a VERTICAL MISALIGNMENT.

One way to understand this is to think of the stereoscopic
deviation as a vector.  In a properly recorded and
mounted stereo pair, this vector is in the horizontal
direction.  By rotating the chips, you are rotating this
vector too, resulting in a vertical component.  This is
a big "no, no" in stereo.  There should not be any
vertical deviation in a stereo pair.  

Following this vector analogy, it is clear that the amount
of this deviation is larger the larger the deviation and the
larger the rotation angle.  For small angles, the deviation
is small and this is where Ken's practice applies... It is
better to tolerate a small vertical misalignment than having
to live with obviously tilted pictures.

Also, it is clear that if the picture is nearly flat, such rotation
is not problem.  You can rotate a 2d print anyway you want!

Will continue in the next message....

George Themelis
http://home.att.net/~drt-3d/


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