P3D Re: "Too much depth"

[Bruce Springsteen <bsspringsteen@xxxxxxxxx>]

This term has always seems a bit vague and misleading to me too.  Abram
(THINK IN ANGLES) Klooswyck described the issue in angular terms, and I
like that.  For normal eye-spacing, the angle of convergence between the
eyes is about 2 degrees when fixing on an object at about 30 times the
"base" (the approx 7 feet of the Realist window).  So to go from zero
convergence at infinity to a point 7 ft away, we swing the eyes through a
2 degree convergence change.  More than that may be more or less
comfortable, depending on who you are.  But at some point the near object
becomes "unviewable", thus:  The brain is able to take the rivalrous
information between left and right retinal images of the object fixated at
7 feet and magically "fuse" it into a tolerable mental composite - the
phenomonon we call stereopsis.  As the object draws nearer, or as we
increase the base (an equivalent action for my purposes), the angle of
convergence is greater (ultimately approaching 180 degrees for an object
right between the eyes ;-)) and these differences between the left and
right view of a thing become ever greater.  At some point the increasing
discomfort of "merging" it into a sensible mental model breaks down.  This
is "close-up misery" as I understand it.  The deliberate, tolerable
distortion of ortho base intended to draw objects smaller and closer will
at some point deteriorate into a complete disruption of the cyclopean
image, at some imprecise moment in increasing base-to-object ratio, and
the jig is up, magic is over, game is called on account of headache.  Lots
of old stereo cards exhibit this pathology to some degree. ("Image loss"
is going on too, but this is my thought experiment, and I can ignore that
for now.)

Isn't the problem of "too much depth" really more about the near limits of
stereopsis?  "Doubling" of non-fixated objects isn't a problem, in fact
it's part of the cues for stereo, so that doesn't seem to be the source of
discomfort.  And "swinging" through greater angles from near to far points
doesn't seem in itself to be such a big deal either.  I like my theory. 
Do y'all think it's dumb?

Bruce (I can see both your profiles at once!) Springsteen 

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