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WHY SLIDE FILM?
Rowland Rogers.*
1. What is slide film?
Some wise "gent" once said: "There's nothing new under the sun." In stating this truth, he was a great Har. Now, shde film is new, — except for the fact that the idea is very old.
Slide film is the grandchild of the magic lantern. The magic lantern had a child. Its name is stereopticon. You know it well.
As Granddad Magic Lantern and the Son Stereopticon used a screen on which the images were projected, so does the Granddaughter Slide Film. The better the screen, the better the projected picture. Any good stereopticon screen will do for the slide film. Of course, a reflecting screen for a narrow room and a diffusing screen for a wide one.
There are several standard slide film projectors in use. All make use of the electric lamp as a light source for projection.
The main point of difference between slide film and the stereopticon is this: the stereopticon uses glass slides to hold the photographic image. These slides are ordinarily about three or four inches long. Each is detached or separate from the others. Slide film, on the other hand, makes use of regular motion picture positive film. Each frame of the slide film picture is a movie frame. The image in the frame is f of an inch high by 1 inch wide. Each picture is attached to its preceding and following neighbor. With the slide film one picture follows the other in fixed succession. Each frame is projected separately, but in fixed, continuous order. A correct term to describe slide film would be "still film" as distinguished from "movie film." There is no attempt to give the similitude of motion. One still picture follows another in the sequence of projection without a break or interruption. Each picture may be held on the screen as long as desired. There is no defined rate at which they must be projected. The rate is left to the discretion of the projectionist. He in turn is controlled by the needs of the audience. In other words there is no standard projection speed because none is necessary.
* Picture Service Corp., New York, N. Y.
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