(^38) THREE-DIMENSIONAL PHOTOGRAPHY
Fig. 3-6. The Ryker, a small version of the Wheatstone stereoscope
used for viewing prints up to six inches square, is an aerial photo type
of viewer. Courtesy J. P. Medders.
application, the unit pictures may be as large as 16x20 inches.
A small Wheatstone viewer with prismatic reflectors was made
by Zeiss under the name of Pulfrich. Improved prismatic viewers
have been repeatedly designed for industrial and survey work in
which the pictures are laid side by side upon a table, but the
fundamental principle is the same.
IMPORTANCE OF VIEwERs.-We have spent a considerable
amount of time discussing viewers, for a very good reason, even
though most of them are types which seem to be growing obso-
lete. Success in stereoscopy depends upon the perfection of the
image, so in stereography satisfaction is derived only when the
presentation of the image is flawless The fact that cheap viewers
can, and do, ruin the work of skilled stereographers using fine
cameras, is well known. If the beginner wants to derive the ut-
most satisfaction from stereography, let him first buy the best
viewer he can afford and then obtain the best camera he can for
what remains of his funds. A $30 box camera and a $100 viewer
.)
frankie
(Frankie)
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