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J. Perelman
"Entertaining physics". Book 1.
Chapter 9. Vision one and two eyes


Earlier we said that different images of the same subject, merging in our eye in rapid alternation, create the visual impression of a relief.

The question is: will it only when moving images are perceived immobile eye, or the same will be observed in the equivalent case, when a still image is perceived fast-moving eye?

It turns out, as was to be expected that a stereoscopic effect is obtained in this case. Probably many readers happened to notice that cinematic picture taken from a fast moving train, find an extraordinary relief, not inferior to that which is achieved in the stereoscope. We can directly verify this if you are attentive to the visual impressions which are perceived when driving fast in the car or in the car: the landscape observed, are stereoscopic, the distinct separation of the foreground from the back. Feeling the depth increases considerably extends far more of those 450 m, which are the limits of stereoscopic vision for stationary eyes.

Isn't this is the reason pleasant experience, which gives us the landscape, viewed from the window of a fast racing car? Dal goes back, and we clearly distinguish the vastness spread around pictures of nature. When a fast moving car we were passing through the forest, then - for the same reason - every tree, branch, leaf perceived by us clearly delimited in space, distinctly separated from each other instead of merging into one, as for the stationary observer.

And when driving fast on the road in the mountain country all terrain soil is perceived directly by the eye, the mountains and valleys are felt with tactile plasticity.

All this is available one-eyed people for whom these feelings are brand new, the unknown. We have already noted that for the relief of vision is not necessary, as we usually think, simultaneous perception of different paintings certainly two eyes; stereoscopic vision is realized and one eye, if different picture merge at a sufficiently rapid change [This explains the noticeable stereoscopic cinematographic pictures, if they filmed the train around the curve, and take the subjects were lying in the direction of the radius of the curve. “Train effect”, which we have here in mind the well-known cameraman.].

Nothing is easier than to check said: this will require only a little attention to what we perceive, sitting in the train or in the bus. You will notice, maybe another amazing phenomenon, about which wrote the Dov hundred years ago (indeed, Novo what is good is forgotten!): flashing past the window close objects appear reduced. This fact explains the reason has little to do with stereoscopic vision, namely, that, seeing such a fast-moving objects, we erroneously conclude about their proximity; if the subject is closer to us, as if unconsciously think we - it must be in the nature smaller than usual, to appear the same size as always. This explanation belongs to Helmholtz.

Entertaining physics J. Perelman


System Orphus


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