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1950-51 Theatre Catalog, 9th Edition, Page 278 (258)

1950-51 Theatre Catalog, 9th Edition
1950-51 Theatre Catalog
1950-51 Theatre Catalog, 9th Edition, Page 278
Page 278

1950-51 Theatre Catalog, 9th Edition, Page 278

EXPOSITION BUILDINGS. The Palace of Mines, Metals and Machinerv (above) at the 1989 Golden Gate International Exposition. Entrance pylons (below) at the Great Lakes Exposition of [936.

material. These environmental and facing material factors are given consideration in Table 1 showing recommended levels.

It is extremely important, when considering a material for use on a theatre facade, to know the nature of its surface. A rough surface diffuses reflected light, while a smooth one reflects its specularly. Circumstances usually require that the light be directed upward from floodlights placed below the area to be lighted. If the surface is smooth or specular, the reflected light goes Skyward, and the facade appears dark to the observer on the street. On the other hand, if the surface is rough and the light is diffused, the area appears bright from all viewing positions. It is, therefore, advantageous to select a facing material that has a matte surface or one that has been roughened by appropriate tooling.

Selection and Placement

The selection and placing of Hoodlights is important and deserves careful study. Floodlights are available in sizes to accommodate 100 watts to 1500 watts and in beam spreads from approximately 100 to 1000. Due to reasons of economy, it is advisable to use as large a wattage unit as is consistent with the requirements, but the actual choice is much more complex than this would indicate, for it envolves a study of the surface coverage and the required illumination intensity.

The foregoing point is illustrated by the chart shown in Fig. 1, where a 30a beam is projected, first, perpendicular to the surface to be lighted and, secondly, at an angle with a vertical surface. The pattern on the surface, when the floodlight beam is directed perpendicular to it, is a circle 17' in diameter, whereas the same beam directed at an angle to the surface is an ellipse with a minimum diameter of 24.5' and a maximum diameter of 34.5'. The area of the circle is 223 square feet, and the area of the ellipse is 664 square feet. Since a footcandle is one lumen per square foot, the average number of footcandles on the surface can be determined by the following formula:

Emi Lumens 2

Area of Pattern

If it is assumed that the floodlight is delivering 4,000 beam lumens, the average number of footcandles over the circular pattern is:


and over the elliptical pattern is:

igg : 6 FCS. (approx)

In the event that, under the prevailing relative positions of the floodlights and the surface to be illuminated, a larger pattern of light is required, the obvious solution lies in the use of a wider beam unit; and, similarly, if a higher or lower level of illumination is required, a larger or smaller wattage floodlight is

Footcandles 1 =

: 18 FCS. (approx.)

1950-51 Theatre Catalog, 9th Edition, Page 278