Three-Dimensional Photography - Principles of Stereoscopy

172 THREE-DIMENSIONAL PHOTOGRAPHY

“prison bar” effect, but it did not make the image three dimen-

sional from every convenient point of view. This lenticular idea

was applied to a movie screen after the expenditure of a fortune.

But as could have been predicted, it worked only when the eyes

were correctly aligned with the screen. For that reason it was

dropped only to be re-invented (?) by the Russians after the patent

reprints had been made public. This is the much vaunted Russian

stereo movie. Of course, in Russia it is possible to maintain audi-

ence rigidity by edict, but here the audience pronounces the edict

against the exhibitor.

Now let us consider a few elementary facts:

If stereo is to be seen without any type of viewer, it is clear

that the rays from the left image must reach the left eye, with no

more than a small residue visible to the right eye, and vice versa.

If an integrated stereogram displays stereo relief, this condition

prevails, and you can actually erect a screen into which holes are

cut 2% inches apart. If you apply your eyes to these holes, you

will see stereo. Now imagine such a screen, behind which a num-

ber of people are placed.

1 234567

LRLRLRLRLRLRLR

00000000000000

Here we have seven pairs of eyeholes with 2% inches between
every adjacent pair. If you are looking through pair 4, you will
see stereo, but if you move to the left and look through holes
which include the R of 3 and the L of 4, you will be looking
through an R hole with your left eye and through an L hole with
your right eye-and you will see pseudoscopic relief.
But suppose that all of the even numbered pairs are removed,
and you are looking through pair 3. You move to the right until
your left eye is looking through R of 3; then your right eye is
obscured by the blanked out 4L. Seeing but one image you see
no stereo relief.
Now suppose the screen is removed. You will still have to as-
sume the same positions to see stereo relief, and if you move to
any extent you will either see pseudoscopic relief or neutral
(planar) relief. In no position will the relief be of the clear cut,