Re: freeview/assisted view

[P3D John O. Merritt <JOMERRITT@xxxxxxxxxxx>]

One way to think about why cross-eye free-viewing makes things look
small is the strong cue to perceived distance:  in crossed viewing,
the two eyes' lines of sight intersect closer than the images you
are looking at, so there is a strong convergence cue to go with 
the retinal images that suggests what you're seeing is smaller
and closer.  You can see this effect when you have a persistent
after-image (as from seeing a photoflash); if you look at a far
building, the after-image looks huge against the building, while
if you look at your palm, the same after-image looks tiny, due to
a constant retinal image size that is interpreted as an external
object size as a function of PERCEIVED distance.  

Un-crossed free viewing results in parallel lines of sight for
the two eyes, so this suggests a far away PERCEIVED distance, and
the same retinal images created by the stereo pair are interpreted
as being "life-size"--or bigger.  The other pesky cue of close
ocular focus can be eliminated by wearing "drug-store" reading
glasses, which change the optical distance of the stereo pair.

Is it "free" viewing if you are "wearing" the stereoscope lenses
as a pair of glasses?

JOM


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