290 THREE-DIMENSIONAL PHOTOGRAPHYthe short time necessary to teach people to “read” three dimen-
sional pairs in books and periodicals.
It has been reported that one widely used physics text, using
just this kind of free vision stereo, has been in print some years.
Unfortunately it has been impossible to obtain details before go-
ing to press.*
Sales.-Makers of bulky and heavy products commonly equip
their sales representatives with albums of planar photographs
from which sales are made. This method is admittedly unsatisfac-
tory, but a salesman can hardly carry a five ton truck with him.
Manufacturers have recently experimented with stereo and have
found new possibilities. Stereo proved instantly successful, because
it enables the customer to see, not a worked-up photograph, but
the real thing.
One manufacturer of dresses, whose saleswomen used to carry
two huge trunks of samples, now send them out with a stereo set
and a half dozen samples in a suitcase to demonstrate material
quality and fine details of workmanship. This has resulted in a
sharp upswing of sales because the buyer can actually see all of
the real models.
Manufacturers of specialties for physicians have found stereo
the first practical substitute for personal demonstration. Full
techniques for using new products and instruments are shown
in stereo.
A manufacturer of power shovels sent out a set of stereos
showing various models, small and large, actually engaged in op-
eration. Again stereo scored a huge success in a demonstration.
Throughout the sales field, from the smallest products to the
largest, the use of stereo has proven successful, and is so rapidly
advancing that already most large cities have stereo specialists at
work.
Industria2 Applications.-Stereo is rapidly gaining favor for
making industrial and laboratory records. Mining and engineer-
ing firms make field records; scientists record laboratory experi-
ments; factories have wiring and conduit circuits recorded. In
planning, miniature scale models properly photographed show
the space form of the ultimate full size structure. Whenever a visi-
* “From Gallileo to the Nuclear Age,” Harvey Brace Lemon, University of Chicago
Press.