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1953-54 Theatre Catalog, 11th Edition, Page 262 (226)

1953-54 Theatre Catalog, 11th Edition
1953-54 Theatre Catalog
1953-54 Theatre Catalog, 11th Edition, Page 262
Page 262

1953-54 Theatre Catalog, 11th Edition, Page 262

Truly, workers on the grid method of stereoscopy have a bad time when someone discovers that the images donlt appear satisfactory throughout an audi.t-orium.

Parallax Stereograms

Parallax stereograms are of two principal kinds, one using a grating, or "grid" as the selecting screen placed in front of the images, and the other using a selective screen consisting of small cylindrical lens elements, lenticules, side by side, and running vertically.

The "grid" system was introduced by Berthier in 1896 and was the first form of stereoscopic viewing of still pictures that did not require accessories. The grid consisted of vertical bars with spaces in between. The grid was usually made on a high contrast photographic plate. The picture was a composite which had the two images broken up into bands, the image bands for one eye being interlaced between the image bands for the other. When the grid was spaced at the prescribed distance in front of the composite and viewed from the correct distance, the observer was able to see a binocular view.

The "lenticular" system used a selective screen sometimes registered in front of the images; sometimes directly bonded to the composite photograph. The lenticules do not cut down the reflected light as do the bars in the grid system. In one system, the composite picture is made in a single lens camera which swings through an arc during exposure. The center of the arc is in the plane of the subject.

Lenticular systems are credited to several inventors; among them F. E. Ives

MM ates- y

and his son, Dr. H. E. Ives. Dr. Ives called his the "Parallax Panoramagram." Improvements have been made and further developments carried out by the Americans, Banbenschoeten and Winneek, and the Frenchman Bonnet.

The Zaiiropulo Process

Another invention employing the lenticular principle is that of Jean Zafiropulo, who set out to apply it to the motion picture in particular. The process requires extremely accurate alignment of all elements in photography and projection.

The Zafiropulo process involves the use of a film containing embossed spherical lens elements in its base. Prints must have their lens elements exactly aligned with those in the negative. The lens elements must register with the greatest exactitude in relation to the sprocket holes in the film. Sprocket

- teeth, engaging the sprocket holesy serve

as the basic registration points for picture steadiness. Film shrinkage, which is over one-fourth per cent in the lowestshrink film base, will have to be overcome to prevent lens-element misalignment with relation to the sprocket teeth, and in turn to prevent misalignment of the film lens-elements and the screen lens-elements.

The Zafiropulo process requires only one lens in photography, but is must be of large diameter, from two and onehalf inches to three inches, and such a lens must be of long focus, over six inches in an f/2.5 lens. This is about 153mm compare with 40mm and 50mm lenses, which are the most frequently used in film studios. This long focus lens requires more studio space than is needed in conventional filming.

FRONT VIEW of the Norling camera reveals lho V-shaped variable interaxial control. A! base is a micrometer adjusted to control convergence.

Several other methods have been proposed for the lenticulated (goffered) film process of movie stereoscopy. One is, in essence, an application of the fibeam splitter" principle, differing from it in that it produces a series of bands for each image. One hand, for part of the left eye image, is formed through each lenticule, and another band is formed adjacent to it for the corresponding part of the right eye image, through the same lenticule. The lens must be operated at its widest aperture.

Lippman's "Integral System"

of Siereoscopy

The process of Hintegral" photography discovered by Lippman in 1908 utilized a screen composed of an almost infinite number of small "lens elements" in the form of pin-holes. It affords what most who have seen it consider the ultimate in stereoscopic viewing. It differs from any other system of stereoscopy in that it provides a much larger number of images in the plane of the photograph and ureduces the number of viewing instruments to zero." But Lippmanis integral photographs can be made only as transparencies, and they cannot be projected, nor can they be reproduced to supply copies that have the qualities existing in the original.

These integrated stereograms are made through a screen having a great number of pin-holes, each acting as a camera lens. No camera is used; the pin-holes serving as lenses. The screen can be a photographic image in a contrasty emulsion on the front side of a glass plate with the photographic image produced through it on an emulsion on the back. The holes must be quite small; their size being established by the rules applying to pin-hole photography. There must be a great number of holes for every square inch, and the plates should be quite large, eight inches by ten inches or more.

Exposure is made through the pinholes, and since the effective aperture of each pin-hole is extremely small, long time exposures are essential. They cannot be satisfactorily reproduced; hence copies are not obtainable, and the negative image has to be rendered into a positive by reversal. Viewing should be with a mirror placed so that the proper left-right attitudes of the images can be Obtained.

The nature of the process excludes it from practical usefulness, particularly for motion pictures, but it is an interesting thing with which to play, and can be experimented upon by anyone having the required facilities.

Single Lens Camera for

Motion Picture Sfereoscopy

If two strip stereo films are used. such things as titles can be made by exposing one image, for the required footage, then shifting the camera to expose the other, as is done in making "slide-board" still referred to earlier in this article.

A variation of the principle can be applied to obtain stereoscopic motion pictures, especially aerial shots. The

1953-54 Theatre Catalog, 11th Edition, Page 262