Motion Pictures - 5

Motion Pictures - 5

 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 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 its predecessors even when

subjected to the test of enlargement by projection. This, however, was finally

accomplished, and in the summer of 1889 the first modern motion- picture camera was

made. More than this, the mechanism for operating the film was so constructed that the

movement of the film took place in one- tenth of the time required for the exposure,

giving the film an opportunity to come to rest prior to the opening of the shutter. From

that day to this the Edison camera has been the accepted standard for securing pictures of

objects in motion, and such changes as have been made in it have been purely in the

nature of detail mechanical refinements.