The Encyclopedia Americana (1920)/Cinematograph

CINEMATOGRAPH, (Gr. ‘movement,’ from, ‘to move’), an ingenious instrument introduced about 1895 by two brothers Lumière of Lyons, and founded on the same principle as Edison's kinetoscope—the persistence of vision. The characteristic part of the instrument is a sensitive photographic film or band about an inch and a quarter broad and from 50 feet long upwards, and which is exposed in a cinematograph camera. In this instrument the band passes from the drum on which it is wound around a series of compensating drums into

position behind the camera lens. This lens is equipped with a shutter which opens 16 times in one second, remaining open usually about one one-hundredth of a second, although this time must be much reduced for quick movements like those of a trotting horse. During the time when the shutter is closed the film is pulled forward three-fourths of an inch, presenting a new surface for the succeeding exposure. The entire mechanism is worked by turning a crank-handle at the uniform rate of two turns per second. After exposure the film is developed by the tank method and wound for drying upon a large drum. In order to produce positives from these nega- tives a second sentitive film is exposed beneath it in a suitable apparatus and duly developed. If desired the positive may be conventionally colored by hand; the pictures are too small to be colored in detail. The cinematograph proper is a projecting lantern arranged to show the film pictures in rapid succession enlarged upon a screen. Besides the customary combination of the brilliant light and lenses which constitute a projecting lantern, the cinematograph is characterized by a delicately adjusted apparatus for advancing the film picture by picture in jerky fashion past the aperture behind the lenses at the rate of 16 per second, and a shutter which opens when the film is stationary and closes while it is moved onward. The periods while the shutter is closed are so brief that the eye fails to note it, the previous picture persisting upon the retina of the eye until the next picture appears on the screen. Upon the skill with which this delicate mechanism is regulated depends the steadiness, or freedom from flicker, of the view on the screen. Unfortunately the lenses which condense or concentrate the light used for projecting also condense the heat rays, and the film being of celluloid is quickly ignited if the winding reels pause when the shutter is open. Four or five seconds exposure to the concentrated rays is enough to start a conflagration, often with the most serious consequences. Recently several effective automatic fire prevention devices have been introduced and the newer cinematographs have this very necessary protection.

The moving mechanism for the film is operated generally by hand, as with the cinematograph camera, but in some machines a small electric motor is attached. However, the hand mechanism is much to be preferred if an expert operator is to be had, as he can gauge the speed by the actual effect on the screen and thus compensate for any deviations in the speed with which the original film was made.

The average length of the commercial exhibition cinematograph film is from 600 to 1,000 feet, requiring from 10 to 16 minutes for its presentation on the screen. Some extended subjects occupy three reels, or 3,000 feet, and require 50 minutes for a presentation. It is necessary to the smooth production of the motion picture on the screen that the individual pictures appear at the rate of 16 per second. It is not necessary, however, that the negative should have been exposed at the same rate. For instance, very interesting pictures showing the growth and blossoming of a plant have been produced by making the exposures at intervals longer or shorter—an hour, or even a day between. The film thus obtained in a

period stretching over months is shown in a few minutes on the screen, and the actual motion of the plant as it grows is witnessed by the audience. This latitude in the time within which a film may be exposed affords opportunity for the production of marvel or trick pictures, the camera being stopped while changes are made and started again to make such record as is desired. The continuous exhibition of the film presents the illusion that the picture presented was also a continuous event. Consult Bennett, C. N., ‘The Handbook of Kinematography’ (London 1911); Hopwood, H. V., ‘Hopwood's Living Pictures’ (London 1915); Hulfish, D. S., ‘Motion Picture Work’ (Chicago 1913); Jones, B. E., ‘How to Make and Operate Moving Pictures’ (New York 1916); Talbot, F. A., ‘Practical Cinematography’ (London 1913).