STEREO PROJECTION 197the spectators must be placed in widely spaced positions, which is
a waste of space and disliked by spectators.
- In practical applications it has been found necessary to spot
the seats in irregular “islands” in the auditorium. - At best the stereo effect, while true stereo, produced by two
differentiated images, is somewhat vague and lacks all of the sharp
realism of the conventional stereo. - In any such system, because of its inherent optical character-
istics, there will be positions where either no picture, a flat picture
or reversed relief is seen; and the only remedy is to have the spec-
tator move his head about until he finds the correct position,
which must then be held.
It need hardly be said that under these conditions plus the poor
stereo effect seen, the disadvantages far outweigh those of the
goggles.
STEREO vs. THREE DIMENSION.-It is the vogue these days to
overwork the term “three dimensional.” For example an innova-
tion in motion pictures has recently been widely heralded by press
and radio as “the roundies,” “three dimensional” and the like
when in fact the picture is just as flat as any movie you ever saw.
However, the screen is monstrous and extends in wings at the
sides. Three projectors operate in synchronism to project the gi-
gantic picture. Now because these wings on the screen do extend
outward from the plane of the center section; because the surface
of the screen is not a true plane, it is perfectly correct to say that
the picture is three dimensional. Now consider the modern stere-
ographer who seems to find the word “stereo” somehow old fash-
ioned and has elected to call his work “three dimensional.” Per-
haps the fact that this motion picture technique which has not the
remotest suggestion of stereo, can truthfully be called “three di-
mensional” simply because the screen does extend in three dimen-
sions, he will be satisfied to revert to the older and far more spe-
cific term “stereo.” It might be added in passing that this volume
was given its present title simply because so many people inter-
ested in stereo do not know that the word “stereo” refers to this
type of photography!
THE ScREEN.-Most materials which might be used as a screen
surface, such as glass beads, white enamel, white cloth and the
like, destroy the polarization of a beam of polarized light. If such