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1945 Theatre Catalog, 4th Edition, Page 310 (286)

1945 Theatre Catalog, 4th Edition
1945 Theatre Catalog
1945 Theatre Catalog, 4th Edition, Page 310
Page 310

1945 Theatre Catalog, 4th Edition, Page 310

THE HIGH-INTENSITY LAMP, as exemplified in the 65-ampre Mogul, is utilized in the largest of theatres, with screens 24 feet or more wide. Throwing better than 10,000 lumens of excellent light on the screen, these lamps

employ cored, copper-coated carbons. The estimated over-all operational cost of such lamps is $1 an hour. For

still more efticient screen illumination, the use of coated lenses is urged. (Strong Electric Corporation photo.)

Moderate Size Theatres

The majority of theatres employing screens up to 18 feet in width catering to a more critical patronage accordingly must have projection comparable to that of the best houses, regardless of other operating economies which must be effected.

To supply the requirements of these moderate size theatres, there has been developed the very popular Lkw. highintensity are lamp that projects about 4,200 lumens of snow-white light, a light

possessing the qualities so necessary to the perfect projection of Technicolor pictures.

This 1-kw. lamp, with its associated rectifier equipment, has been produced as a low first-cost item of equipment, which will perform perfectly on singlephase power circuits, since only singlephase poWer is generally available to this type of theatre.

The overall cost of current and carbons in this l-kw. lamp is just 2 cents an hour more than with the low-intensity arc. However, since this high-intensity

THE ONE-KILOWATT LAMP is valuable for use in theatres employing screen sizes up to 18 feet in width. It is a high-intensity arc which proiects about 4,200 lumens of snow-white light. Such light possesses the desirable qualities necessary for the most satisfactory proiection not only of black-andswhite pictures, but of Technicolor productions as well. Over-all operational cost is about 29 cents an hour. (Strong Electric Corporation photo.)


lamp projects twice as much light as the low intensity one, the actual cost of light is less for a lumen-hour than in the instance of the low-intensity arc.

Following these same calculations the very large theatres, with screens up to 20 feet in width, require 7,300 lumens to maintain a screen brilliancy of 10 foot lamberts as required for deluxe projection.

These large theatres require a highintensity arc, burning up to 70 amperes and employing a 14-inch reflector. The carbon costs for these lamps are 13 cents an hour. In addition, these large lamps require 6-tube rectifiers, a copperoxide rectifier, or a motor-generator set with a current consumption of 4-kw., making a total overall operating cost of 29 cents an hour for current and carbon.

The "Palaces"

Extremely large theatres using tremendous screens of 24 feet or more, having a screen area of at least 419 square feet and requiring over 10,000 lumens of light-to say nothing of drive-in theatres with screens of 40 feet in width and theoretically requiring 30000 lumens ehave always experienced difficulty in obtaining the desired screen brilliancy of 10 foot lamberts. The largest condenser-type, high-intensity projection lamps operating at 130 to 175 amperes with an over-all cost of current and carbons of $1 an hour has been the most powerful equipment available. However, these lamps produce only about 10,000 lumens, as compared with the 30,000 lumens desirable.

Future developments point toward a larger lamp of higher projected-light volume and employing 16-inch reflectors with 9-mm., copper-coated, high-intensity carbons operating up to 90 amperes, in which the position of the arc crater, relative to the focal point of the reflector, will be maintained constant by means of a supplementary optical and electrical system which controls the speed of the carbon feed motors. These future lamps, when used in combination with the new, high-speed, coated projector lenses, hold promise of at least partially solving this projection problem.


All of the arcs mentioned here necese sarin require direct current for their operation; however, alternating current is generally the only type of electricity available in theatres, as a.c. is the only means of transmitting electric power over long distances. Therefore, each theatre must have its own means of converting the a.c. power to direct current for use at the arc. The various types of arcs each require a definite and specific relationship between arc amperage, arc voltage, and the amount of line voltage resistance or ballast for stable operating of the arc.

Low-Intensity Lamps

In the case of the low intensity arc, operating between 20 and 30 amperes, the potential drop across the arc is 50 to 55 volts. However, for stable operating of this low-intensity arc, the dc. power supply should be at least 80 volts

1945 Theatre Catalog, 4th Edition, Page 310