P3D Re: toe-in

[Linnstaedt@xxxxxxx]

 ron labbe <ron@xxxxxxxxxxxx> writes,
"... The [hemi-]sperical back of the eye does not introduce keystone
distortion as does the plan[a]r back of the camera.">>

Agreed, our eyes do not introduce keystone distortion in the usual sense.
However, IMHO, there IS perspective distortion.  Anyone attempting fine detail
work has experienced the problem.  Try this:  Fix your gaze upon an object and
rotate your head while keeping your eye on the object.  Do you see distortion?
I do, within the object and also in its relation to other objects (parallax).

Regarding toe-in, the movement of our eyes most certainly does introduce
"distortions".  Yet our wonderful brains correct for these (to a certain
extent), utilizing these distortions as visual cues.  When someone speaks of
"cardboard" effects, I am convinced it can be significantly explained by these
missing depth cues.  I propose naming the cardboarding effect, "planar
distortion".

When looking at reality closer than infinity, the eyes toe-in and in so doing,
one sees not from a different vantage but different perspective.  One's eyes
see partially around the object, but only so long as the gaze is focused upon
that object.  On looking at a different object, the perspective changes so the
first object changes roundness (and fusion).  This dynamic cannot occur
through the stereoscope, because the photograph is frozen.  So the stereoview
is practically identical to two photographs of cardboard flats arranged at
differing depths.

Toe-in presents so much greater problems for stereophotography than it solves.
Within limits, it can assist realism, but at the potential for an un-fuseable
stereograph.

Robert Linnstaedt


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