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color of its light is very close to that of ordinary sunshine. The yellow flame carbon gives a light rich in red and green, but having comparatively little spectrum yellow or blue. The sensation of yellow light is produced by the combination in the eye of the red and green light. The violet in this light is fairly strong. The red flarae arc gives a light rich in red and in spectrum yellow, and has a fair amount of blue. The so-called ''blue" flame carbons a,re designed to be especially rich in far ultra-violet beyond 3000° Angstrom units. This far ultra-violet is practically absent in sunlight and likewise in the white flame arcs ordinarily used in photographic work. The near ultra-violet light is very important photographically with sunlight and skylight, and with the white flame arcs. The ultra-violet of the white flame is largely in the region longer than 3 500° Angstrom and it efficiently goes through ordinary glass.
An important improvement has been the use in photographic lamps of metal coated flame carbons, especially on the holder end. This metal coating reduces the holder drop in voltage from about half a volt to 1/20 of a volt so that a holder designed for 5 ampere use can, with metal coated carbons, be used at 20 and 30 amperes with long, excellent service.
American white flame carbons, both in our tests and those throughout the United States have shown 10 to 15 per cent better efficiency of hght and longer life on the average than the foreign carbons. This is because of superior knowledge and skill that the American carbon manufacturers have as regards the making of these flame carbons. This condition of superiority has been maintained for several years.
6. Discussion of General Advantages of the White Flame Lamps for Photography
The following ten points repeat a few of the advantages of the flame lamps for photographic artists; the greatest efficiency; best color duplicating daylight; instant response when the current is turned on; less unsteadiness from fluctuating line voltage; wearing nart of smallest cost per unit ; most rugged to all kinds of mechanical and electrical abuse and to adverse weather conditions; lowest cost of installation and operation; can be used for spot lighting or with screen for diffuse lighting or with reflector for indirect lighting; largest candlepower per single unit and maximum portability in proportion to candlepower.
7. Special Lighting Effects
In considering the lighting of moving picture studios, we will consider first over-head lighting and then side lighting. In regard to overhead lighting there are two classes — diffuse and concentrated. The diffuse lighting is often obtained in the glass studios by use overhead of flame arcs which occupy only a small area and allow considerable of daylight to enter the scene. The concentrated overhead lighting is secured by mounting in a large reflector a score of
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