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

THE SIGHT OF THE GIANTS

When the subject is very far away from us, then 450 m, the distance between our eyes cannot affect the difference of visual impressions. The distant buildings, distant mountains, the landscapes seem so flat. For the same reason, and the luminaries of heaven seem to be all at the same distance, even though the Moon is much closer than the planet, and the latter is immeasurably closer than the fixed stars.

In General, for all objects that are located on 450 m, we completely lose the ability directly to perceive the relief; they seem right and left eye are the same as those of 6 cm, which is separated by the pupils of the eyes from each other. too tiny distance compared to 450 m it is Clear that stereoscopic pictures obtained under these conditions, completely identical and can not give the stereoscope illusion of relief.

But really easy to help: need to photograph distant objects from two points of mutual destruction which is greater than the normal distance between the eyes. Looking at such pictures in the stereoscope, we will see the landscape the way I see it, if the distance between our eyes was much higher than usual. This is the secret of obtaining stereoscopic images of landscapes. Commonly it is seen through a magnifying prism (with convex sides), so that such relief stereosemke often drawn to us in natural size; the effect is striking.

The reader may have guessed that conceivable to arrange the two visual system of pipes through which you can see the relief of the landscape directly in nature, and not on the pictures. Such devices - stereotomy - indeed there are: two tubes separated them by a distance greater than the normal distance of the eyes, and both images enter the eye through reflective prisms.


Stereoscopic optic pipe.

It is difficult to describe the sensations that you feel when you look in such instruments, " they're extraordinary! All nature is transformed. The distant mountains are visible, trees, rocks, buildings, ships at sea - all krupitza, all convex, arranged in infinite space, and not lying flat on the screen. You directly see how far a vessel which in the ordinary pipe seems to be fixed. In this form would be submitted to our earthly landscapes fabulous giants.

If the increase of the pipes 10-fold, and the distance of the lens 6 times higher than the normal distance between the eyes (i.e., equal to 6.5 * 6 = 39 cm), the perceived image 6 * 10 = 60 times more plastic than when viewed with the naked eyes. This means that even items deleted at 25 km, find another noticeable relief.

For land surveyors, sailors, gunners, travelers such telescopes positively indispensable, especially if they are provided with a graduated scale by which you can measure the distance (stereoscopic rangefinders).

Prismatic binoculars the Zeiss also gives this effect, since the mutual distance of its lenses more than the normal distance between our eyes.


Prismatic binoculars.

In the theatre binoculars, on the contrary, the distance between the lenses is reduced to a weakening of the terrain (so that the scenes did not seem apart).

Entertaining physics J. Perelman

 




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