Three-Dimensional Photography - Principles of Stereoscopy

(Frankie) #1

TRICK WORK 237
with flash to preserve the smoke quality. In this instance any blur
of movement will detract from the result.
Take notice of the position of the cloud. The target shooter’s
method of orientation is good. Imagine the picture a clock face
and mentally tabulate positions as “one o’clock” “five o’clock”
and the like. Also imagine a series of circles drawn around the
center of the picture, perhaps four of them dividing the field into
a center spot and three concentric circles. Then a position in the
upper right corner would be “ 1 : 30 in 4” or if not in the extreme
corner “i:30 in 3”. That is, the position of half past one and in
the third ring, counting the center spot as 1.
The second shot is divided into two exposures of the girl, but
she maintains her pose and does not move between the two expos-
ures, which makes the work far easier. But it must be remembered
that any obvious detail in her background will be visible, so as a
rule it is advisable to pose her against a black background which
will fill the camera field (which may be masked around the edges
if desired).
The diminution is computed. Suppose the model is 64 inches
tall and you want her to be 16. That is i:4. You then proceed to
make the two successive shots of her using a four times normal
base. The stereo camera has one base already, so you expose with
the right lens, then move the camera three times the base (Realist
= 3 x 70 = 210 mm), to the left and make the other exposure.
A special top for the tripod permitting the side motion while
retaining strict parallelism is not difficult to make and means all
the difference between success and failure in this type of work.
Refer to Fig. 1, the right exposure to be made first. The sight
over the right lens is turned until the center of the table lies
across the vertical cross wire, and the camera with sights tilted
until the far edge of the table coincides with the horizontal cross
wire.
The model 0 is then moved until the vertical cross wire bisects
her figure and her feet rest upon the horizontal wire, for example.
The exposure is made.
Without moving the camera, the left sight is brought to bear
upon the center of the table, and the model moved until the
vertical cross wire again bisects her figure. The horizontal wires
serve the same purpose in both. The second exposure is now

Free download pdf