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1947-48 Theatre Catalog, 6th Edition, Page 353 (339)

1947-48 Theatre Catalog, 6th Edition
1947-48 Theatre Catalog
1947-48 Theatre Catalog, 6th Edition, Page 353
Page 353

1947-48 Theatre Catalog, 6th Edition, Page 353

INTERIOR VIEW of the C-7 carbon arc lamp, showing the 14-inch reflector. arc alignment. arc stabilizer, door battles, and carbon drip cup, reveals the absence of any working parts outside the housing. Highly visible manual control. with its associated ammeter, is shown at the left. The

Single- feed - screw lamps have long been discredited in the light projection field-by the exhibitor because of their constantly varying quantity and quality of light, and by the projectionist for the same reason plus the necessity for constant manual adjustment of the controls.

But even the larger-capacity Suprex lamp operating at the top limit of 65-68 amperes with a 14-inch mirror may fail to provide adequate screen illumination because it is not optically correct-%hat is, it is not properly designed to cos ordinate with the new fast lenses. Most of the large-capacity lamps now in use suffer from this deficiency.

The primary requisite for any Suprextype lamp, irrespective of current capacity and solely because of the critical nature of this type of arc, is the combination of precise control of both negative and positive carbons (only possible by means of a dual feed), and a highly efficient optical system. This combination must be provided for in the design and built into the lamp; there can be no rec vamping of the elements once the lamp is built.


It is just this happy blending of hairline arc control and line optical system inherent in its design that enables the Ashcraft 070 to encompass the Wide current operating range that it does. From 40 to 65 amperes, and at all intermediate levels, control units and optical system work as a team to produce fine projection.

It is fallacious to attempt to utilize a fast lens of the order of f/2.0 or better

ARC STABILIZER METHOD: Positive carbon (1) extends through loop (3). Magnetic flux (2) exerted at (4), forcing up gas ball (5). Ideal arc is when edge of flame (6) is almost straight.

new proiection arc embodies several major teatures and many others which constitute a departure from the conventional design of equipment. The lamp operates on 4D to 65 amperes, with a dual feed so that both positive and negative carbons are led independently by separate screws.

with a lamp the optical system of which is f/2.3, f/2.5, or' f/2.8, which is the range covered by most lamps now in operation. The speed of the slower unit, whether lens or mirror, determines the over-all optical elticiency of the lamp. A hybrid combination of fast lens and slow mirror, or vice versa, is not etTicient projection.

0n the C-70 lamp no mechanical changes of any nature are required to effect the transition from the lowest to the highest current levels (40 to 65 amperes). Using an 8smm.-7-mm. Suprex carbon trim at 65 amperes, the C-70 will not only enable an optical speed of f/1.9 but will compare favorably in terms of quantity and quality of light output with a straight highintensity lamp using 13.6-mm. carbons and pulling 125-130 amperes.

Considering the steadily increasing number of color film releases, no exhibitor, irrespective of how small a screen area he utilizes, can afford to be Without the protection given by this reserve lamp current capacity.

Contributing greatly to the efliciency' of the 0-70 are control is a radically
1947-48 Theatre Catalog, 6th Edition, Page 353