Intrinsic Brightness
Description
This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
Intrinsic Brightness
By intrinsic brightness is meant the amount of light emitted per unit surface of the light source. Table XII gives the intrinsic brightness of several light sources.
Table XII. Intrinsic Brilliancies In Candle-Power Per Square Inch
Source | Brilliancy | |
Sun in zenith | G00,000 500,000 2,000 | Rough equivalent values, taking account of absorption |
Sun at 30 degrees elv. | ||
Sun on horizon | ||
Arc light | 10,000) to 100,000 | Maximum about 200,000 in crater |
Calcium light | 5,000 | |
Nernst "glower" | 1,000 | Unshaded |
200-300 | Depending on efficiency | |
Enclosed arc | 75-100 | Opalescent inner globe |
Acetylene flame | 75-100 | |
Welsbach light | 20 to 25 | |
Kerosene light | 4 to 8 | Variable |
Candle | 3 to 4 | |
Gas flame | 3 to 8 | Variable |
Incandescent (frosted) | 2 to 5 | |
Opal shaded lamps, etc. | 0.5 to 2 | |
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