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1953-54 Theatre Catalog, 11th Edition, Page 254 (218)

1953-54 Theatre Catalog, 11th Edition
1953-54 Theatre Catalog
1953-54 Theatre Catalog, 11th Edition, Page 254
Page 254

1953-54 Theatre Catalog, 11th Edition, Page 254

THIS DRAWING represents a simple slide board.

eter demands a lens of long focal length. Consequently, this particular process is limited to still stereograms. Because'of the large size of many stereograms used this way, projection would introduce many problems. Viewing boxes are used instead.

Stereographic Drawings

and Paintings

A more or less obscure form of the three-dimensional art is the rendering of stereographic drawings and paintings. As a teaching aid, Professor John T. Rule, of the Massachusetts Institute of Technology, has introduced such novel drawings for celestial navigation and solid geometry. They provide the student an unusually effective portrayal of spatial relationships. Some of Professor Rule,s drawings have been published in vectograph form as an adjunct to classroom texts.

In the illustration field, Paul H. Stone has produced a number of striking stereograms. Stone has a theory which makes interesting reading on the subject of how the eyes work: }

Our two eyes scan every pin-point of a scene, as rapidly as a television beam; from top to bottom, side to side, and, most important, from near to far. It is less the focus of each cornea than the convergence of the two beams of vision which telegraphs a sense of depth, of distance to the brain.

I believe the actual muscular pull on the eyeballs, whether they are crossed toward each other or straightened to parallel, and infinity, is the recording device which informs the brain about

AN ILLUSTRATION of the principle oi the Kennedy stereoscopic single lens camera is seen.




the length of the convergent triangle. Hence the brain can infer with reasonable accuracy, depths, from a few inches to the better part of a mile.

Versatile Stereo Camera

While the amateur has available a wide selection of stereoscopic cameras and accessories, there are no well-designed cameras for the professional. If he wants to go into stereoscopy, virtually the only thing he 'can find is an old Stereo Graphic in a second hand store, or if he is fortunate, one of the excellent Icas. But neither of these has all the features required by the serious worker.

A professional stereoscopic camera should contain, as principal features, a means for varying the lens interaxial and a means for converging the picture axes on any desired plane.

Probably the easiest way to show what a versatile stereoscopic camera is like is to describe one of several types designed by the author. The assembly compriSes two camera bodies mounted on a common base. Each has its own lens, but the lenses are mounted in a unique

absolute requirement for projected stereograms. If not precisely aligned, the three-dimensional pictures cannot be viewed with complete visual comfort, and the goal of the serious worker is and should be nothing short of complete visual comfort in viewing.

The mask on the right has a small hole close to the picture area that permits a cue mark for the purpose of quickly identifying it, thus facilitating the assembly of the pairs. This camera is used mostly for making color threedimensional slides, although it has been used to make master black-and-white negatives for vectographs and anaglyph stereograms.

One arrangement that can be employed to attain the variable interaxial feature is illustrated. In this arrangement a partially-reflective, partially-transmittive mirror is used, one camera being placed behind the mirror, the other being placed so that it receives the image by reflection from the partially silvered first surface of the mirror.

This method permits the interaxial-to, be varied from zero to the limit per DIAGRAM ILLUSTRATES an arrangement of components at a special still picture stereoscopic camera.



way, pointing off at right angles, one to the left, the other to the right. In front of each lens is a first surface mirror whose face is 45 degrees to the lens axis. A right handeleft hand screw provides a means for moving the camera bodies together or apart, thus controlling the interaxial spacing. This spacing can be varied from one and one-half to six inches, permitting satisfactory setting for objects as close as four and one-half feet, using seven inch lenses. The assemblies which carry the lenses and front mirrors are movable for a small distance forward and backward. This makes it possible to converge the picture axes to any plane desired. The images are framed within metal masks which are mounted so they can retract for the insertion of the film holder's dark slide. These masks accurately define the picture areas, and if the convergence control is properly uSed, the masked margins provide precise registration for mounting. It should be emphasized that precise alignment of the pictures is an


mitted by the size of the mirror. Of course, the "left eye" camera (in the arrangement shown) will have its image reversed left for right, but that is unimportant because the negative can be turned back to normal in printing.

The mirrors should be the pellicle type, such as we used in some colorseparation still cameras. Satisfactory results have been obtained with thin glass mirrors, 1/32 inch thick or thereabouts. A thick glass mirror cannot be used because a second reflection will show in the image picked up by themirror. If a thin glass mirror is used, the secondary reflection will not be separated far enough from theprimary image to become discernible if the mirror is mounted at about 57 degrees.

If a pellicle mirror is used it must be mounted in a frame that will afford the facility for stretching it taut.

Taking Stereo Still Pictures

The stereo still photographer is confronted with just about the same prob THIATII CATALOG l953-54
1953-54 Theatre Catalog, 11th Edition, Page 254