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1950-51 Theatre Catalog, 9th Edition, Page 341 (319)

1950-51 Theatre Catalog, 9th Edition
1950-51 Theatre Catalog
1950-51 Theatre Catalog, 9th Edition, Page 341
Page 341

1950-51 Theatre Catalog, 9th Edition, Page 341

High-intensity arcs are available both for direct current and for alternating current operation. Both reflector and condenser type optical systems are used for carbon arc projection lamps. Outlined in Table I are the characteristics, operating conditions, and performance of the principal high-intensity carbon arc projection systems.

Descriptive Table of Carbons

Table I also shows the types and sizes of carbons normally used with the different lamps and the current ranges over which they are operated. The data on screen light output of the different types of lamps have been taken from material previously published, and represent approximately the optimum that can be obtained from high-quality, well-adjusted equipment. The ranges of screen light cover the extremes of current and screen distribution values, ranging from those characteristic of the focal adjustment which produces maximum light, on the one hand, to those pertaining to the rather uniform screen distribution of 80% side-to-center ratio on the other hand.

Many factors influence the exact light output and screen brightness from equipment in a specific theatre. However, in order to obtain an approximate idea of the sizes of screens which can be illuminated to the recommended standards of brightness, screen light values for a Screen distribution approximately intermediate between those just described have been combined with a projector shutter of 50% transmission (900 openings) and a diEusing screen of 75% reHection factor. In this manner, approximate ranges of screen sizes which can be illuminated to minimum and maxi mum recommended brightness have been set up as shown in Table I.

One-Kilowatt Retlector Lamps

These lamps are the smallest in size and lowest in output of the high-intensity projection systems. They employ the popular copper-coated ttSuprex" carbons, which are operated non-rotated in horizontal, coaxial alignment. In spite of the fact that their light output is approximately twice that of a low-intensity lamp, their operating cost is no higher than that of a low-intensity arc. As shown in Table I, they are capable of illuminating screens 17 to 21 feet in width to the recommended levels.

In view of the foregoing facts, there seems to be no reason why even the smallest theatre should not have daylight-quality, high-intensity carbon arc illumination of its screen with bright ness levels equivalent to those obtainable in the finest houses.

"Suprex" Carbon Retiector Lamps

These popular lamps, employing the well-known copper-coated ttSuprexii and "Orotip" C carbons burned non-rotated in coaxial alignment, were first introduced in the early thirties. They are used by many thousands of theatres in the middle-class size. Like the one-kilowatt lamps, they are very economical to operate, particularly in relation to the amount of light produced. Table I shows that they are capable of lighting 18 to 27-foot screens to maximum brightness and 22 to 32-foot screens to minimum brightness.

Rotating Reflector Lamps

Before the advent of the lamps employing itSuprex2 carbons non-rotated,


there were available the so-called "HighLowi, lamps which were also of the refiector type and employed a bare rotating positive carbon with the negative carbon placed at an angle. These lamps, however, were replaced almost

Table I-High-lntensity Carbon Arc Projection Systems

Type of Lamp Ito/Tech" Lamps

fOne-Kilowattii All. and TLC.

iiSuprcxii Carbon Reflector


7mm x 12 or 14" "Suprex" (4) 7 and 8mm x 12

or 14-" and 9mm

Approximate Brightness Screen Light Range-Amps. Lumens (1)

Carbons Current

N egati re

58-65 A.C. 40 D.C. 42-85

6mm x 9" ttOrotipii C 6, 7 and 8mm x 90 iiOrotipl, (I

x 14" "Suprex"

Rotating High (3) Intensity

Condenser Lamps

Rotating High (3) Intensity

Rotating High (3) Intensity

9 and 10mm x 20" 7731;" and Him" x H.l. Projector

13.6mm x 22" H.I. Projector

13.6mm x 22" uHitex" Super

75-100 9" TOrotipii

7m" or "g" x 9" 125-150 30rotip'i

Trio" 01' VJ" x 9"

Heavy Duty "0rolip"







Aprox. Screen W7idth W'hich Can Be Illuminated to Recommended Brightness Levels for Indoor Theatres (2)

Maximum Minimum

Brightness 9 FootLamberts

14 Foot Lamberls

17 feet 21 feet

18-27 22-32

25-30 (3) 30-35 (3)

25-30 (3) 30-35 (3)

30-33 (3) 35-40 (3)

(1) Screen lumcns without shutlcr. film, or filtcrs of (my kind; f/2.0 treated projection lcns; sec JOURNAL OF SOtllETY OF MOTION PICTURE ENGINEERS, January, 19-17, page 76, and June. 1950, page 726, [or more complete details and test conditions.

(2) Assuming 50% shutter transmission and 75% screen reflection factor.

(3) These systems may require protection from heat on film. and any

light losses [or this or any other reason will influence corres ponding screen widths. For example. a 10%) loss in light will reduce by approximately 5% the screen width which can be illuminated

to a given brightness. (4) Used for both electrodes on A.C.


hi ,
1950-51 Theatre Catalog, 9th Edition, Page 341