POLARIZED LIGHT APPLIED TO STEREOSCOPY 217ning vertically would enable anyone simply to look through them
to see the transparency in full relief. Of course the pairs of strips
would have to be separated to prevent the use of the opposed
strips which would produce a pseudoscopic effect.
Vectograph as a Photograph.-If the Vectograph is to be used as
a normal photograph for mounting in a book or the like, one side
of the finished product is flowed with an aluminum paint of spe-
cial grade. This provides a non-depolarizing reflecting backing
for the print. This is in every way similar to the doretype which
was at one time highly popular as a portrait medium.
Vectograph in Medicine.-One of the principal roles of the Vec-
tograph is in medicine. At present stereo X-rays must be viewed in
special viewers which are extremely large and cumbersome. The
usual viewer will occupy a floor space of about three by six feet,
and stand five feet high. The surgeon who is to follow the X-ray
as a guide in operating must study it beforehand and then take
only a “flat” film into the operating room. If the X-ray is a Vecto-
graph and the surgeon is provided with half-goggles of polarizing
films, he can observe the X-ray in full relief while actually oper-
ating.
GENERAL APPLICATION.-In fact, there are many more applica-
tions of this process, some of which were proven during World
War I1 when hundreds of Vectographs were made from aerial
films. The process is attractive to stereographers, even though it
does lack the orthostereo quality as do all “viewerless” processes.
It is an interesting type of stereogram and for many purposes it
has certain advantages over the conventional double stereogram.
There is hardly a question of superiority, rather a question of the
suitability for any specific purpose. When orthostereo is de-
manded, a viewer must be used because it is an integral part of
the ortho technique, but when it is simply desired to obtain
stereo relief without ortho proportions, the simplicity of the Vec-
tograph has much to recommend it. The fact that the viewer
(which resembles a pair of sun glasses) and several prints may be
carried in the pocket is an unquestionable advantage.
Also see Chapter 19.