Edison, His Life and Inventions [208]
and thereby result in a reproduction of the movements. Two very serious difficulties lay in the way of actual accomplishment, however--first, the production of a sensitive surface in such form and weight as to be capable of being successively brought into position and exposed, at the necessarily high rate; and, second, the production of a camera capable of so taking the pictures. There were numerous other workers in the field, but they added nothing to what had already been proposed. Edison himself knew nothing of Ducos, or that the suggestions had advanced beyond the single centrally located photographs of Muybridge and Marey. As a matter of public policy, the law presumes that an inventor must be familiar with all that has gone before in the field within which he is working, and if a suggestion is limited to a patent granted in New South Wales, or is described in a single publication in Brazil, an inventor in America, engaged in the same field of thought, is by legal fiction presumed to have knowledge not only of the existence of that patent or publication, but of its contents. We say this not in the way of an apology for the extent of Edison's contribution to the motion-picture art, because there can be no question that he was as much the creator of that art as he was of the phonographic art; but to show that in a practical sense the suggestion of the art itself was original with him. He himself says: "In the year 1887 the idea occurred to me that it was possible to devise an instrument which should do for the eye what the phonograph does for the ear, and that by a combination of the two, all motion and sound could be recorded and reproduced simultaneously. This idea, the germ of which came from the little toy called the Zoetrope and the work of Muybridge, Marey, and others, has now been accomplished, so that every change of facial expression can be recorded and reproduced life- size. The kinetoscope is only a small model illustrating the present stage of the progress, but with each succeeding month new possibilities are brought into view. I believe that in coming years, by my own work and that of Dickson, Muybridge, Marey, and others who will doubtless enter the field, grand opera can be given at the Metropolitan Opera House at New York without any material change from the original, and with artists and musicians long since dead."
In the earliest experiments attempts were made to secure the photographs, reduced microscopically, arranged spirally on a cylinder about the size of a phonograph record, and coated with a highly sensitized surface, the cylinder being given an intermittent movement, so as to be at rest during each exposure. Reproductions were obtained in the same way, positive prints being observed through a magnifying glass. Various forms of apparatus following this general type were made, but they were all open to the serious objection that the very rapid emulsions employed were relatively coarse-grained and prevented the securing of sharp pictures of microscopic size. On the other hand, the enlarging of the apparatus to permit larger pictures to be obtained would present too much weight to be stopped and started with the requisite rapidity. In these early experiments, however, it was recognized that, to secure proper results, a single camera should be used, so that the objects might move across its field just as they move across the field of the human eye; and the important fact was also observed that the rate at which persistence of vision took place represented the minimum speed at which the pictures should be obtained. If, for instance, five pictures per second were taken (half of the time being occupied in exposure and the other half in moving the exposed portion of the film out of the field of the lens and bringing a new portion into its place), and the same ratio is observed in exhibiting the pictures, the interval of time between successive pictures would be one-tenth of a second; and for a normal eye such an exhibition would present a substantially continuous photograph. If the angular movement
In the earliest experiments attempts were made to secure the photographs, reduced microscopically, arranged spirally on a cylinder about the size of a phonograph record, and coated with a highly sensitized surface, the cylinder being given an intermittent movement, so as to be at rest during each exposure. Reproductions were obtained in the same way, positive prints being observed through a magnifying glass. Various forms of apparatus following this general type were made, but they were all open to the serious objection that the very rapid emulsions employed were relatively coarse-grained and prevented the securing of sharp pictures of microscopic size. On the other hand, the enlarging of the apparatus to permit larger pictures to be obtained would present too much weight to be stopped and started with the requisite rapidity. In these early experiments, however, it was recognized that, to secure proper results, a single camera should be used, so that the objects might move across its field just as they move across the field of the human eye; and the important fact was also observed that the rate at which persistence of vision took place represented the minimum speed at which the pictures should be obtained. If, for instance, five pictures per second were taken (half of the time being occupied in exposure and the other half in moving the exposed portion of the film out of the field of the lens and bringing a new portion into its place), and the same ratio is observed in exhibiting the pictures, the interval of time between successive pictures would be one-tenth of a second; and for a normal eye such an exhibition would present a substantially continuous photograph. If the angular movement