The processes of fixing, washing, and drying of the negatives are carried on with the greatest care due to the high production cost represented in the film, and the necessity for preserving the film for long periods of time. Particular attention is paid to the treatment of the wash water to eliminate undesirable alkali compounds, and to the maintenance of proper humidity in the dry ing process.
For many purposes, duplicates are made from original nega tives. These are made by printing upon special duplicating films prepared by impregnating a fine grain positive type film with dyes, usually either lavender or red in colour. These prints are referred to in the industry either as "lavenders" or "red masters," the latter being a recent development with a much finer grain emul sion than is used for "lavender" masters. From the master positive, whichever type is used, another print is made upon pan chromatic negative film, this print becoming the duplicate nega tive from which prints may be made which are sufficiently like the original so as to make it difficult to tell them apart. The new fine grain duplicating stocks are rapidly replacing the laven der films throughout the world.
Printing.—After development of the picture and sound track, the first print is made from each. These first prints, known as rushes or dailies, are assembled on separate reels, the sound track being printed on a separate film from that of the picture. They are then viewed by the various departments concerned with the production of the picture, and if approved, are turned over to the editorial department for cutting. The scenes, if found unsatisfac tory because of photography, sound, acting, make-up, etc., are retaken as soon as possible. As the production of the picture con tinues, the film editor assembles the picture and sound track prints in continuity according to the script, until he has a com plete picture a few days after the last scene is taken.
The majority of picture printing machines in use today are of the continuous type, the negative and positive films being moved continuously past a narrow, illuminated slit, being held in close contact at the exact point of illumination. Another type moves the two films intermittently in a manner similar to both the camera and projector movements, the positive film being exposed through the negative by a light which is cut off by a shutter while the films are being moved. Projection printing is also employed, especially for lap dissolves, montage shots and trick photography, the negative image being projected onto the positive film through an optical system, the films being separate.
The intensity of illumination in all types of printers is changed from scene to scene to insure an even exposure of the print, as the negative scenes frequently vary through a wide range due to in accuracies in exposure and development. Notches are cut in the edge of the film following each splice, these notches tripping a mechanism which operates an electric relay circuit and changes the printer light according to predetermined settings.
Sound track prints are always made on a continuous type printer, and for faithful reproduction of the sounds recorded on the negative, the printer movement must be entirely free from mechanical disturbances, contact at the point of printing must be nearly perfect, and the source of illumination absolutely constant. Modern sound printers include accurately adjusted optical sys tems which focus a slit of light less than .003in. wide and approxi mately o.ioin. long at the point of contact, have ultra-violet filters to utilize more effectively certain spectral characteristics of the positive film stock, and have mechanical filters which remove all traces of gear disturbances, which, if present, are printed onto the film with the sound from the negative.