Edison, His Life and Inventions [209]
of the object across the field is very slow, as, for instance, a distant vessel, the successive positions of the object are so nearly coincident that when reproduced before the eye an impression of smooth, continuous movement is secured. If, how- ever, the object is moving rapidly across the field of view, one picture will be separated from its successor to a marked extent, and the resulting impression will be jerky and unnatural. Recognizing this fact, Edison always sought for a very high speed, so as to give smooth and natural reproductions, and even with his experimental apparatus obtained upward of forty- eight pictures per second, whereas, in practice, at the present time, the accepted rate varies between twenty and thirty per second. In the efforts of the present day to economize space by using a minimum length of film, pictures are frequently taken at too slow a rate, and the reproductions are therefore often objectionable, by reason of more or less jerkiness.
During the experimental period and up to the early part of 1889, the kodak film was being slowly developed by the Eastman Kodak Company. Edison perceived in this product the solution of the problem on which he had been working, because the film presented a very light body of tough material on which relatively large photographs could be taken at rapid intervals. The surface, however, was not at first sufficiently sensitive to admit of sharply defined pictures being secured at the necessarily high rates. It seemed apparent, therefore, that in order to obtain the desired speed there would have to be sacrificed that fineness of emulsion necessary for the securing of sharp pictures. But as was subsequently seen, this sacrifice was in time rendered unnecessary. Much credit is due the Eastman experts--stimulated and encouraged by Edison, but independently of him--for the production at last of a highly sensitized, fine-grained emulsion presenting the highly sensitized surface that Edison sought.
Having at last obtained apparently the proper material upon which to secure the photographs, the problem then remained to devise an apparatus by means of which from twenty to forty pictures per second could be taken; the film being stationary during the exposure and, upon the closing of the shutter, being moved to present a fresh surface. In connection with this problem it is interesting to note that this question of high speed was apparently regarded by all Edison's predecessors as the crucial point. Ducos, for example, expended a great deal of useless ingenuity in devising a camera by means of which a tape-line film could receive the photographs while being in continuous movement, necessitating the use of a series of moving lenses. Another experimenter, Dumont, made use of a single large plate and a great number of lenses which were successively exposed. Muybridge, as we have seen, used a series of cameras, one for each plate. Marey was limited to a very few photographs, because the entire surface had to be stopped and started in connection with each exposure.
After the accomplishment of the fact, it would seem to be the obvious thing to use a single lens and move the sensitized film with respect to it, intermittently bringing the surface to rest, then exposing it, then cutting off the light and moving the surface to a fresh position; but who, other than Edison, would assume that such a device could be made to repeat these movements over and over again at the rate of twenty to forty per second? Users of kodaks and other forms of film cameras will appreciate perhaps better than others the difficulties of the problem, because in their work, after an exposure, they have to advance the film forward painfully to the extent of the next picture before another exposure can take place, these operations permitting of speeds of but a few pictures per minute at best. Edison's solution of the problem involved the production of a kodak in which from twenty to forty pictures should be taken IN EACH SECOND, and with such fineness of adjustment that each should exactly coincide with
During the experimental period and up to the early part of 1889, the kodak film was being slowly developed by the Eastman Kodak Company. Edison perceived in this product the solution of the problem on which he had been working, because the film presented a very light body of tough material on which relatively large photographs could be taken at rapid intervals. The surface, however, was not at first sufficiently sensitive to admit of sharply defined pictures being secured at the necessarily high rates. It seemed apparent, therefore, that in order to obtain the desired speed there would have to be sacrificed that fineness of emulsion necessary for the securing of sharp pictures. But as was subsequently seen, this sacrifice was in time rendered unnecessary. Much credit is due the Eastman experts--stimulated and encouraged by Edison, but independently of him--for the production at last of a highly sensitized, fine-grained emulsion presenting the highly sensitized surface that Edison sought.
Having at last obtained apparently the proper material upon which to secure the photographs, the problem then remained to devise an apparatus by means of which from twenty to forty pictures per second could be taken; the film being stationary during the exposure and, upon the closing of the shutter, being moved to present a fresh surface. In connection with this problem it is interesting to note that this question of high speed was apparently regarded by all Edison's predecessors as the crucial point. Ducos, for example, expended a great deal of useless ingenuity in devising a camera by means of which a tape-line film could receive the photographs while being in continuous movement, necessitating the use of a series of moving lenses. Another experimenter, Dumont, made use of a single large plate and a great number of lenses which were successively exposed. Muybridge, as we have seen, used a series of cameras, one for each plate. Marey was limited to a very few photographs, because the entire surface had to be stopped and started in connection with each exposure.
After the accomplishment of the fact, it would seem to be the obvious thing to use a single lens and move the sensitized film with respect to it, intermittently bringing the surface to rest, then exposing it, then cutting off the light and moving the surface to a fresh position; but who, other than Edison, would assume that such a device could be made to repeat these movements over and over again at the rate of twenty to forty per second? Users of kodaks and other forms of film cameras will appreciate perhaps better than others the difficulties of the problem, because in their work, after an exposure, they have to advance the film forward painfully to the extent of the next picture before another exposure can take place, these operations permitting of speeds of but a few pictures per minute at best. Edison's solution of the problem involved the production of a kodak in which from twenty to forty pictures should be taken IN EACH SECOND, and with such fineness of adjustment that each should exactly coincide with