Three-Dimensional Photography - Principles of Stereoscopy

CORRELATION OF CAMERA AND VIEWER 67
intercept the original Pn plane at D” and G” instead of at D and
G. As U’G” must equal A”C” and occupy a corresponding lateral
pusitiurr, we find side D%” located just kah!kay bmem the
eyes and side A“C”. Thus we locate the viewed image D’%‘G’
which is seen to be nearer the observer than normal. Because the
lateral width is truly the same as the original but the distance
only half, the apparent size of the object is increased. As might
be expected with the general condensation of depth, the altitude
of the triangle is lessened and the degree of loss is one-half. Thus
the degree of distortion keeps step with the original differences
throughout.
In the following diagrams of the triangle series, the various
measuring points are not numbered, only the triangle and the
planes being indicated. The measuring lines are shown but not
indexed.
Figure 4-6 shows in the graphic triangle form the error which
was illustrated by Figs. 4-3 and 4-4. As it is just the reverse of the

!

fS d

~ c“C

i 1

Fig. 4-7. Camera focus

greater than normal.

Fig. 4-8. Viewing stereo-

gram made with camera

focus greater than nor-

mal.