HYPERSTEREO 263cedure, wholly upon unsupportable grounds, namely that the
rules of orthostereo are violated and that the subject is presented
as an insignificant miniature instead of in its original grandeur.
Neither argument will stand searching inquiry.
In all fairness however it must be admitted that the normal
stereogram exhibits all of the relief in such distant scenes that
would be perceptible to the eye if the scene were actually viewed.
Because we are accustomed to “read” into distant scenes the
relief indicated by the extrinsic depth factors, the normal stereo-
gram is about as satisfactory as direct vision. However, the pur-
pose of the hyperstereogram is to reproduce the scene in a better
manner than it could be seen by direct vision. Any such attempt
to improve upon nature is condemned by many, but any such
reasoning would rule out the extremely attractive field of photo-
micrography, so the objection is hardly tenable.
As for the laws of orthostereo, it is quite true that these are vio-
lated, but it is significant that those who are the most bitter an-
tagonists of hyperstereo upon these grounds habitually violate
the principles of orthostereo even when there is no reason for
doing so. Although the necessity for having the focal lengths of
the lenses of both camera and viewer identical is recognized, if
orthostereo is to be achieved, this is rarely found in practice. Even
when allowance is made for permissible variation, it will be found
that practice violates the principle to an extent far beyond the
permissible. Specifically, there is a widespread habit among stere-
ographers, of using a Gxi 3cm camera with three-inch lenses and
then mounting contact prints from these negatives for viewing in
the Brewster stereoscope which ordinarily has lenses whose focal
length is between six and eight inches. Fortunately, the widespread
use of 35mm cameras and associated viewers is eliminating this
abuse.
The fact is that, as shown by repeated experiment, violations of
the ortho principle of considerable degree have no effect which is
obvious when the stereogram is viewed. This is unfortunate as
far as the law is concerned, but as it is true, the insistence upon
orthostereoscopic conditions should be limited to those special
instances where it is highly desirable, as in scientific record, Ob-
jection should be limited to those instances in which the viola-