Full Moon - Unusually Big & Bright - May 5

[Skeptic Ginger]

OK, so someone else in another forum is arguing with me about parallax beyond very close objects. He's a jerk who isn't dumb but prefers short, "you're wrong" replies to actual learn-something-new dialogue.

As I said in my original response, stereopsis isn't the source of the illusion, because stereopsis is negligible at those distances. But somehow cvering one eye tells the brain to interpret the scene differently. Therefore a new illusion takes over in dispelling the relative size illusion. Its interesting that covering one eye ma,es the brain interpret the scene efifferently even though stereopsis isn't what fooled the brain in the first place.

The entirety of 3D perception includes factors other than the parallax effect, but only the parallax effect is directly removed by switching to monocular vision. It's a fascinating insight into perceptual psychology.

I probably shouldn't have answered, "Riiight".

But when I said he contradicted himself (see above bold) and asked for some hypothesis or explanation, if it wasn't parallax, what was it, he got snitty.

I could just be reading something completely wrong in the post. It wouldn't be the first time.


Anyhoo, I looked further into the matter and thought I'd share:

Stereoscopic perception of real depths at large distances

Our experiments clearly demonstrate a binocular enhancement of apparent depth magnitude, even at large observation distances. This binocular advantage was evident for both observation distances (20 and 40 m) and for almost all of the target depth separations tested ...

Thus, it is clear that stereopsis supports some perception of metric depth (albeit compressed) at large observation distances (i.e., it provides more than a simple “closer further” discrimination).

What these researchers found was stereoscopic depth perception was detectable without other cues at a distance of 40 meters and when one added additional cues, the depth perception was more acute. So both, parallax and additional visual cues appear to affect the illusion.

It's best seen with this graph where monocular vision negates depth perception even with other visual cues.


If not parallax, then it's difficult to explain how the effect was detected in the dark without additional visual cues, and it is difficult to explain why when relying solely on the visual cues on a 2D image there is no difference between monocular and binocular vision.


So does anyone here have an hypothesis that would explain these findings other than parallax?


I plan to see how monocular vs binocular vision affects the Moon-horizon illusion when the horizon is a greater distance than the trees and buildings the Moon rises over as seen from my yard. But it's cloudy here, so it'll have to wait unless it clears up by tonight.