Three-Dimensional Photography - Principles of Stereoscopy

CLOSE-UP STEREOGRAPHY 241

aperture, and this is duplicated in the sharp edge of the mount

aperture. This is the real reason for avoiding extreme close-ups

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2A 20

IA. The normal lenses produce images in which the close-up object is

recorded upon the film outside the center.

1B. When transposed, this stereogram shows the close-up images nearer

than the centers, causing the loss of a wide band at each end.

2A. With prisms before the lenses (or prismatic close-up lenses), the
rays are so deviated that the nearby object is recorded at the film
center.
2B. This centering of the images avoids the loss of bands at sides.

without compensation. When such a close-up object is photo-
graphed, the plane area occupied by that object is not at all dupli-
cated in the two images, so there is a relatively wide “ghost” band
at the sides of the viewer field. If objects at a distance are also
included, it will be seen that these side bands shrink to an im-
perceptible degree when looking at the distant object, but return
when the vision returns to the close-up object.
Those familiar with stereo disregard this phenomenon as in-
evitable when both extreme close-up and distance appear in the