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1953-54 Theatre Catalog, 11th Edition, Page 256 (220)

1953-54 Theatre Catalog, 11th Edition
1953-54 Theatre Catalog
1953-54 Theatre Catalog, 11th Edition, Page 256
Page 256

1953-54 Theatre Catalog, 11th Edition, Page 256

ILLUSTRA'HNG HOW nearby object images are cut of! when image axes don't converge on objects.

to fill a large screen does one more thing that the individual and personal stereoscope never can accomplish, and that is to create the feeling that the scene is big. While it is perfectly true that the picture on the screen may be of the same angle of view as the same picture mounted in a stereoscope, and that theoretically there should be no physical reason why the scene elements should not appear the same in each, looking through a stereoscope very often gives one the feeling that he is looking at a miniature, and he has that feeling whether or not the scene was photographed normally. Perhaps the fact that the picture is itself small in dimension gives rise to the feeling that the original scene must likewise be small.

Most stereograms made today are in the form of slides which are looked at through a hand-held viewer or seen as projected images. The hand-held, selfilluminated viewer is a familiar device. Some viewers, including the Realist, have provision for a variable lens spacingea valuable feature that contributes to visual comfort. The Stereo-Realist image is seven-eighth inch wide and 15/16 inch high, but there are other mask sizes such as one inch wide by seven-eighth inch high, and one and one-eighth inches wide by 15/16 inch high. All can be mounted in the standard one and fiveeighth inches by four inches glass, which will go into the slide carriers of the new stereoscopic projectors. For professional type slides, each member of the stereo pair is made up in standard three and one-fourth inches by four inches glass, and put into a holder which accommodates the two members side by side.

Projection of stereo slides requires the use of polarizing filters, one for each lens, an aluminum surfaced screen, and polarizing threesdiniensional viewers.

The projection filters are arranged with their polarization axes slanting 45 degrees from the vertical, one slanting to the right, the other to the left. The viewers have polarizing filters which also "slant" in the same manner. Consider the light from the right hand lens, with a polarization axis slanting toward the left. The light renected from the screen can be seen through only the right-eye polarizing filter, because it too has the same left-hand slant while the left-eye filter has a right-hand slanty 90 degrees from that of its mate. Thus the "righteye" light is blocked from reaching the left (lye, and the uleft-eye" light is blocked from reaching the right eye.

The reason for using an aluminum surfaced screen is that this type of sure face will not disturb the polarization of the light. A fabric or glass-beaded screen will cause the polarization to disappear. the light to become ordinary light again. The rcsult is that the tWo images will be seen by both eyes, and will look jumbled like a double exposure.

Plastic screens arc now available for rear projection of polarich light stereograms. Rear projection adds a brilliant quality quite dillicrcnt from the rcilcction method, although a uhot spot" may be disturbingly apparent unless arrangements are made to kccp thc spectatorls





eyes and the projection axis from lining up.

For extremely dramatic stereogram presentations, a picture 18 inches wide can be thrown by a projector containing two 1200 watt bulbs and a pair of 18 inch f/3.8 lenses. With a picture this wide, an audience is usually given to itch-ingll and bah-ing" with delight and surprise as each successive stereogram appears on the screen.


Hyperstereoscopy is the term applied when an interaxial base several times normal is used. It has often been employed in mountain photography and serves admirably to reveal distant details in relief. The base employed is often 100 yards or more. Care must be taken not to include any foreground, otherwise one image will contain elements not present in the other, and it will be impossible properly to fuse the stereogram. Since mountains can usually be depended upon to stand still for a long time, there is time to set up the camera and to transport it from one extreme of the interaxial base to the other. But clouds are not so considerate in itstaying put" as mountains, so the exposures should be made on a cloudless day.

Hyperstereogramsy properly made, require that certain rules for determining the interaxial be followed. The simplest one is

d X I)

D' d where d is the distance to the nearest object, I) the distance to the farthest and 50 thc divisor whose use assures success.

Keeping within the limits prescribed will give the stcreograms the post. vivid relief possible without eyestruin in vimving.

llypcrstereoscopy has been employed to makc stereograms of bodies in thc solar system, whcrc cven the mcan diamcter of the earth often proves insufficient as an interaxial base. Stcrcograms of most plancts have been made and inter csting data has thus been obtained. 1n + 50

cluded has been the discovery of a planetoid, which was found as the result of this type of stereoscopic survey, and it was appropriately named Stereoscopia in tribute to the method. Stereograms of the moon have been made which reveal intimate details of its craters and seas. Some of the most remarkable have been those of Saturn and its rings, one pair of which required the movement of Earth through space that was the equivalent of an interaxial base of about 1,000,000 miles, which is the distance traversed by our planet in its orbit during a 24 hour period. Other stereograms of this planet made with an even greater base disclosed clearly the separation of its unusual rings one from another and from the planet.

A word of warning concerning hyperstereoscopy: it does not seem to produce satisfactory results for close-up objects, and certainly will not do so if such stereograms are projected. This is so for close objects because the angle formed between the two lenses at the base and the object is so great that it throws distortion into the images. For instance, photographing a golf ball at a distance of one foot and using a wide interaxial will produce a stereogram which makes the golf ball appear egg shaped, and golf balls having this shape give neither the player nor the viewer any pleasure.

High speed stereoscopic photography is often employed for special purposes. Such stereograms often reveal things not readily apparent in a lint picture. They are particularly useful in the study of machine elements in motion and for other kinds of research. A series of three high-speed itstrobcll shots were made for United States Rubber Company to prove the behavior of a golf ball. These shots were made on letachromc film at a speed of one-millionth of a second, using one of Professor Harold 1'3. liidgcrtonls newcr flash units. Professor llldgcrton and Henry Lcstcr worked together in obtaining the shots. The projcctcd pictures showed no Hegg-shape" distortion which would have resulted if


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1953-54 Theatre Catalog, 11th Edition, Page 256