American cinematographer (Jan-Dec 1926)

December, 1926 AMERICAN CINEMAT O G R A P II E K Twenty-one DUPLICATION ^/MOTION PICTURE NEGATIVES I Cniitinurii7from Pace 9) posed area surrounded by an area of less exposure developed up denser than it should, while small areas surrounded by areas having greater exposure developed up with less density than they should. The explanation of the phenomena is simple. In the first case, the developer acting on the small exposed area diffuses into the surrounding gelatin as it becomes exhausted, and fresh developer diffuses into the spot from all sides thus accelerating development. In the other case, when the small area has had less exposure than its environment, the opposite conditions hold, development of the small area being actually restrained by the reaction products diffusing into it from all sides. If development is stopped at an early stage, the defect is quite pronounced. If, however, development is continued until the image has reached maximum contrast, fresh developer has time to soak into the film from the outside and the irregularity is smoothed out. The "Mackie" line has a similar explanation to the uEberhard" effect and is really a manifestation of the latter on a scale that is easily discernable in the projected picture as a sort of halo surrounding the images of dark objects against light toned backgrounds. To Be Avoided It is particularly desirable to avoid these defects in the duplicating process because, like graininess, they are cumulative, and they are largely responsible for the "duped" appearance of prints made from duplicate motion picture negatives prepared on a high contrast emulsion. Attempts have been made to find a developer or developing conditions that would permit development to a low degree of contrast without producing the defects but with no success. Apparently, the only way to eliminate the fault is to use an emulsion which when nearly fully developed will give the contrast or gamma required. Inasmuch as motion picture negative and positive films do not compjetely satisfy the rigorous demands made on a duplicating material* efforts were made to produce something more suitable. It was found that the charac Supplicd as $^0 special equipment on DeVry and other M. P. Cameras <•<%<« Since 1884, manufacturers of fine View Cameras and Lenses. Write for complete catalogue of fine apparatus for the Still Studio. UNDLACH-MANHATTAN OPTICAL GO. 1 900 Clinton So., Rochester, N. Y. Subscribe to American Cin ematogr apher 4 in. Iris Combination and Sunshade Trueball Tripod Head FRED HOEFNER Cinema and Experimental Work 5319 Santa Monica Blvd. (rear) Los Angeles, Calif. GLadstone 0243 SCHEIBE'S PHOTO-FILTER SPECIALTIES Are now popular from coast to coast, and in some foreign countries. If my many varieties do not always fill the bill, tell me your wants and I will make them on special order. Always at Your Service GEO. H. SCHEIBE 1636 Lemoyne St. DUnkirk 4975 Los Angeles, Cal. FOR RENT BELL HOWELL AND AKELEY CAMERAS With or Without Cameramen SEIDEN CAMERA EXCHANGE 729 Seventh Ave. N.Y.c. B ryant 3 95 1 Wire us for any | New York Scenes you may need Prices Reasonable CLUBBING OFFEB Subscribed for separately, Camera Craft, and the American Cinematographer will cost a total of $4.50 per year. As a special clubbing offer, both magazines may be had at a total price of $3.40 per year. American Cinematographer 1219-20-21-22 Guaranty Bldg. Hollywood, California