ELEMENTARY STEREOGRAPHY 3two eyes which are separated hy a distance of 65mm, more or less.
It is obvious that, inasmuch as the two eyes are in different posi-
tions, we have an individual point of view for each eye. It also
follows that the aspect of any scene must be slightly different from
these two points of view, even though the amount of difference
is so slight as to be hardly noticeable.
If two photographs are made from two points of view separated
by a distance similar to that between the eyes, two photographs
will be obtained, and these two will respectively correspond to
the visual image of each of the two eyes. If these two images are
then viewed in such a manner that each eve shall see its own
image and not the other, then we have the conditions of direct
stereoscopic vision duplicated, and instead of seeing the two
images as such, we shall see the single, three-dimensional image
of normal direct vision.Fig. I-1B. How It Works. The same three posts as seen by a
stereo camera. Note that the two lenses each being at one side,
show all three posts, but they “see” the two opposite sides of
the row. Viewed in a stereoscope, the posts are seen in a straight
line, but in depth.Our problem then is two-fold. We must make the two photo-
graphs from separate points of view, and we must so look at these
pictures that each eye sees only its corresponding picture. To that
end the whole art of stereography is directed.
There are refinements of technique, and there are limitations
which are rigidly enforced under certain circumstances, but for