International projectionist (Jan-Dec 1950)

the emulsion, it may be varied within rather wide limits by the time of development and by the type of developing agent used. A gamma of 1 is arbitrarily set as the normal contrast-factor of a photographic image. An image having a gamma less than 1 may be rich in detail, but lacking in normal contrast range. Such an image has a flat, "washed-out" appearance. But when an image has a gamma greater than 1, contrasts are exaggerated, and delicate detail in the highlights and shadows of the image may be utterly lost. If a negative is developed to a gamma of 1, it is necessary to develop the positive print to a gamma of 1 in order to obtain an overall, or resultant, gamma of 1. Soundtrack negative is ordinarily developed to a gamma of about 0.50 in order to avoid distortion from photographic causes. In order to obtain an overall gamma of 1 in the print, the soundtrack positive must be developed to a gamma of 2.00: 0.50 X 2.00=1.00 Certain electrical losses in the recording amplifiers, however, have the same result as reduced contrast of the soundtrack image. In order to overcome these losses, a positive gamma of about 2.15 is required. This gives an overall soundtrack gamma of: 0.50 X 2.15=1.075 or, roughly, 1.08, which is considered satisfactory. The picture image poses a somewhat similar problem. A slight exaggeration of pictorial contrast is an artistic advantage, and it also counteracts a loss of picture contrast inherent in projection. So instead of being developed to a gamma of 0.50 like the sound negative, the picture negative is developed to a gamma of about 0.65. Whenever the positive is developed to a gamma of 2.15. the picture has an overall gamma of: 0.65 X 2.15=1.3975 or, approximately, 1.40. Precise gamma control is admittedly a far cry from guesswork and personal taste in the matter of developing motion picture prints, but frankly, it cannot be said that the present-day picture images are more beautiful than those which graced the silent screen. Film-Developing Machine A film-developing machine is a formidably complicated affair. The main part of it is made up of a series of large tanks containing the various solutions through which the film is conducted in succession by a bewildering array of rollers and sprockets. The leader of blank film used for threading up the developing machine is approximately 2000 feet in length! As the machine is run continuously for many hours at a time, each roll of film to be developed is spliced to the end of the one preceding it while operations are in progress. A virtual reservoir of film upon which the machine can draw during the time needed to make the splices is provided by a film "elevator" at the film-feeding end of the machine. It would, of course, be ruinous to the film to stop, or even to retard a developing machine while film is being processed. The film first enters the developing bath. The time of development is regulated by the threading of the flanged rollers which carry the film through the bath in a number of vertical loops. If a comparatively short devoloping time is required, the film is threaded to by pass certain of the rollers, thereby decreasing the number of loops immersed in the solution and the time at which any one part of the film remains in contact with the liquid. After leaving the developing bath, the film passes through a rinse of pure water, and from that to the fixing bath. This is followed by one or more tanks in which the film is washed and, in some cases, chemically-treated to harden the emulsion and hasten drying. The final washing removes traces of processing chemicals which, if permitted to remain in the emulsion, would cause serious stains. Final Developing Stages After passing from the last tank, the film is drawn into a battery of tall, glassdoored drying chambers. In these compartments the film passes over top and Stan, frenfrvitKcuice with STAR CORE STAR CORE, exclusive feature with the \Z"°\™ ,X" ?" w°rld/"!>rT ' the lorgeil theatres in the U. 5. Lorraine Carbons — a manufatturing throuohout the world u.e Lorraine cor process that increases the performance -Featured in our horizontal feed Of the Carbons. copper tooled carbon., A more brilliant, steadier, more con w«ite ton oisrmeunoN o*r sistent white light — more economically PADDf-lUC IMP ...proven facts as shown by tests vnllDUIw. INvi made under actually operating con BOONTON, N.J. CARBONS, INC. NEW YORK: 234 WEST 44th STREET WITH ANY LAMP IN ANY SIZE THEATRE Jr <C. -c^ ■ ^ -S0r Or *P 1 THIS IS WHAT tZOCt WANT! Customer satisfaction— the theato owner's # 1 asset. Create it by using CENTURY PROJECTION AND SOUND SYSTEMS. For the smallest to the largest Drive-in— for harmony of color tone and picture brilliance, 'Stm^ Sold through recognized theatre supply dealers CENTURY PROJECTOR CORP. New York, N. Y. INTERNATIONAL PROJECTIONIST January 1950 33