10 THREE-DIMENSIONAL PHOTOGRAPHY
The images are viewed through black channels or tunnels,
another instance of the most desirable condition. The lenses are
of adequate dimensions and are provided with motions for focus-
ing and for interpupillary adjustment, The focusing is by thumb
wheel, and the interpupillary by lever. This viewer thus includes
all of the features essential for stereo viewing at its best.
TDC VIEWER.-ThiS viewer is also made of polished black
plastic, but more nearly resembles a pair of binoculars. The
Fig. 3-3. TDC stereo viewer, companion to the
Vivid camera and one of the Eeast costly of the
quality viewers.ocular lenses are mounted in the binocular fashion and focusiqg
is done by the central wheel of binocular type.
It is self-illuminated with a switch which may be locked in
place for continued viewing. The translucent switch button serves
as a pilot to show when the lamp is burning.
Access to the interior for servicing is gained by simply raising
a hinged cover.
This viewer takes the American standard stereo slide which
measures iGx4 inches, in either glass or cardboard mounts.
BUSCH-VERASCOPE VIEwER.-In conformity with American prac-