When viewing stereoscopic images, you can do without any of the device: you just need to train yourself accordingly to direct the eye. The result is the same as using a stereoscope, with the only difference that the image is not increased. The inventor of the stereoscope Wheatstone originally used this natural method.
I am attaching here a series of stereoscopic images of gradually increasing complexity, which are advised to try to address directly, without a stereoscope. Success is achieved only after a series of exercises [it Should be noted that the ability to see stereoscopically - even in the stereoscope - is not given to all people, some (for example, cross-eyed or accustomed to working only one eye) completely incapable of it; to others it is given after prolonged exercise; and finally, third, mostly young people, learn this very quickly - in a quarter of an hour.].
Start with the simple picture of a pair of black dots. Keep them before your eyes and within seconds I took his gaze from the interval between spots; make such an effort seemed willing to consider the subject, located behind the figure. You will see very soon, not two, but four spots - mugs will be split. But then the extreme points will go far, and the interior will converge and coalesce.
A few seconds not take his eyes from between spots - both black spots will merge into one.
If you repeat the same with these two figures, in the latter case, at the time of the merger will see before him like the inside of a long pipe, stretching.
Repeat the same with this pair of drawings. Achieving merge, go to the next exercise.
When these images will merge, you will see a like pipe inside, stretching.
Having done that, you can skip to the next picture; here you. must see hanging in the air of a geometric body.
These four geometric body merging the image seem as if floating in space.
This figure will give you a long stone corridor of a building or tunnel,
Long horizon in the corridor.
and in this picture you can admire the illusion of transparent glass in the aquarium.
The fish in the aquarium.
Finally, the last figure before us is a picture of the sea.
Stereoscopic landscape of the sea.
To learn how this directly examining the paired images relatively easy.
Many of my friends have mastered this art in a short period of time, after a small number of samples. Nearsighted and farsighted, wearing glasses, can not remove them, and look at the image as consider every picture. Try to move up or move away from the eyes of the drawings, until you get the proper distance. In any case it is necessary to do experiments in good light - it greatly contributes to the success.
Learning to consider without a stereoscope drawings reproduced here, you can use a learned skill for viewing in General, stereoscopic photos, without the need of a special device. Those stereoscopic images, which are printed next, also you can try to look for simple eye. You do not have just overly fond of this exercise, so as not to tire the eyes.
If you fail to acquire the ability to manage your own eyes, you can, for lack of a stereoscope, to use the glasses for farsighted - need to glue them under the holes in the cardboard so that only look through the internal edge of the glasses, the images should be placed somewhere in the wall. This simplified stereoscope quite reaches the goal.