Three-Dimensional Photography - Principles of Stereoscopy

70 THREE-DIMENSIONAL PHOTOGRAPHY

Figure 4-1 0 illustrates the significant rays for the condition
wherein the camera base is less than normal. The broken line in
fp-fp indicates that portion where the two bases of the camera
overlap. In Fig. 4-11 note that the original position of the object
lies along the line which bisects the two visual axes. In short, the
direction of the image is identical with that of the original object,
but it seems to have been moved farther away. The net result is
that of a larger object removed into the distance. As D is beyond
the limit of the diagram it is not shown.
The greater the stereo base, the greater will be the parallax.
Also, the nearer any object is to the eye, the greater is its parallax,
and conversely. In Fig. 4-11 the decreased parallax has given the
appearance of an object farther away, while the undiminished
perspective gives to that apparent distance an apparently greater
object size.
Figure 4-12 shows a base which has been increased by 50 per-

fP

Fig. 4-12. Camera base greater

than normal.

Fig. 4-13. Viewing

stereogram made with

camera base greater

than normal.