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New 13.6-Mm Hitex Super HighIntensity Carbon
BY R. M. BUSHONG AND W. W. LOZIER
NATIONAL CARBON Div., UNION CARBIDE AND CARBON CORP. FOSTORIA, OHIO
Summary — The new 13.6-mm Hitex super high-intensity carbon for operation at 170 to 180 amp in condenser-type lamps is described in comparison with the former 1 70-amp super. Data show that the Hitex super carbon gives the possibility of more light, more economical operation because of longer life and a marked improvement in efficiency of light production. Spectral energy and color data show that the light from the Hitex super has a higher color temperature than from the old super.
THE TASK of providing adequate illumination on the largest screens used for the projection of motion pictures is one which has presented a continual challenge to the manufacturers of the equipment involved. Many large indoor theaters have never had as much light as was needed to obtain the results desired. The problem has been intensified in more recent years with the advent of many large-screen outdoor theaters which have much less light available on the screen than necessary to bring them up to the desired levels of screen brightness. The use of audience viewing areas several times larger than indoor theaters has necessitated the use of considerably larger screens. Projection screen areas are approximately four times as great for outdoor as for indoor theaters and consequently require four times as much light to achieve the same screen brightness. It cannot be definitely stated that outdoor theaters, with their different circumstances and surroundings, should have the same brightness as indoor theaters; but there is no doubt that most of them could effectively utilize much more light.
The condenser type of lamp employing rotating positive high-intensity and super high-intensity carbons is widely used by large screen theaters. The first step in the field of super high-intensity projection for large theaters came in 1936 when the 13.6-mm National super high-intensity carbon was introduced.1 This carbon was designed for operation at 180 amp and produced more light more evenly distributed on the screen than carbons previously available. Further
PRESENTED: October 11, 1949, at the SMPE Convention in Hollywood.
JUNE, 1950 JOURNAL OP THE SMPTE VOLUME 54 725