Putting the "Frustum" in "Frustumerated"

DU was right in comments to my last post. Pointing both cameras at the same place (midway between the robots) results in almost identical left- and right-eye images:

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If you look very closely at the full-size image you can see the red/cyan separation along the antennae, but there is essentially no 3D effect at all.

He mentioned "photons," which leads me to suspect this may be related to how when you look through a telescope and cover half the objective lens with your hand, you see the exact same thing you were seeing before but half as bright, when what you should see is half of the image and then a very large hand. I hate physics.