Three-Dimensional Photography - Principles of Stereoscopy

THE STEREOSCOPE 33

side of the box. This permits the lenses to be focused for any
individual vision.
Variable Separation.-The generally accepted standard stereo
separation is 65mm, but human eyes may be separated by either
as little as 55 or as much as 75, with a variation of 5mm in either
direction relatively common. Anatomists usually accept 62 ‘/2 as
the average interpupillary separation, Thus we find that while
most cameras and viewers conform to the stereo standard of
65mm, the Verascopes of Richard conform to the anatomical
standard of 621/2mm.
It is desirable, and almost essential, that the viewer lenses and

Fig. 3-5. Telebinocular. One of the most satis-

factory of the Brewster type viewers. This is the

instrument used in the laboratories of the Stereo

Guild for all stereograms of abnormal separa-

tion, such as the old “parlor” type of view.