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Page:Popular Science Monthly Volume 90.djvu/851

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Popular Science Monthly

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��cranks his machine the film is fed through in a series of rapid jerks, the shutter action being almost continuous. Sixteen pictures are made on each foot of film.

The cameraman, having completed his work, the film is delivered to the developing department. Gen- erally a small piece is clipped and de- veloped to deter- mine light and ex- posure conditions so that the entire film may be treated accordingly and not spoiled.

The developing is done in large tanks. The film is wrapped around large light frames for convenience. Thus mounted it is easily dipped into the bath, and examined without

���Cementing together the make a picture of the

��the direct contact of fingers. When the negative has been developed it is placed in the fixing bath. After that it is thor- oughly washed in clean water. The de- veloping and fixing are generally done in two-hundred-foot lengths. It is difficult to handle any greater length.

Large drums made of light metal and wood are used for drying the film. These drums revolve slowly, thus throwing off water adhering to the back of the film and exposing the emulsion side to a constant current of hot air. The drying room must

��be clean; for even the smallest particle of dust on the film will be magnified many times when the picture is screened. For this reason many special devices ha^•e been installed in modern dr\ing rooms to keep them absolutely free from dust and dirt.

In printing the positive from the negative the ser- vices of real ex- perts are required; uneven work will produce a bad "flicker" on the screen. Printing has been so highly developed that the old annexing "flicker" has al- most disappeared. As in making or- dinar}^ pictures the emulsion side of the negative is brought into con- tact with the positive film and is exposed to the light. Artificial light is used because it is more easily controlled than sunlight. The printing machines used work on the same principle as the motion picture camera with the exception that they "take" tAvo rolls of film, both the positive and the negative. In developing the positive

��200-foot lengths of fihn to standard 1000-foot length

���Photographing the titles and subtitles on films from block-letter signs, with a regiilar motion-picture camera

��Printing the positive from the negative. The printing is d<»ie by artificial light

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