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352 Transactions of S.M.P.E., Vol. XIII, No. 38, 1929
Because of the liiglier efficieiic}^ the new lamps have less filament, hence smaller sonrce dimensions than the old. This means control of beam within smaller limits. The reduction in the linear dimensions of the source is of the order of one-fifth.
Fewer equipments will be required. Moreover, it is possible to place them advantageously^ so as to secure improved lighting effects. Where higher intensities are desired, they can be readily obtained since more equipment can be installed in a given space.
Of greatest significance to the motion picture industry is the saving of many, many thousands of dollars in production expense annually, which the new developments make possible, through the reductions in lamp, energy and equipment costs.
Lamps of the new construction are now available in the 5 and 10-kw. sizes, used in motion picture studio lighting, and in certain other lamps used for other services.
DISCUSSION
Mr. Coffman: Do I understand that the higher the wattage of the lamp the greater its efiicienc}^ ?
Mr. Egeler : Yes, that is true. The higher the wattage of the lamp, the greater the current, which means a larger filament wire is used ; it can be operated at a higher temperature for a ^iven life than the smaller diameter wire. Up to this time, the blackening has been a limiting feature in high wattage lamps.
Mr. Strickler : I want to ask how the life of the lamps averages. Do they average one hundred hours, above, or below? •
Mr. Egeler: We know incandescent lamps have individual lives which are above and below the average. The life we assign to the lamps is the average figure, for these high wattage lamps, 100 hours. Our tests show average lives alDove, rather then below the design figure.
Mr. Loveland : Will not the sagging of the filaments greatly facilitate the blackening of the lamps, especially pear shaped lamps ?
Mr. Wright : Sagging of the filament would not have the effect of increase in blackening ; on the contrary, as the filament sags, the temperature decreases, and the rate of evaporation also decreases.
Mr. Palmer : Figuring on the average life of one hundred hours, what is the cost of the lamp per hour?
Mr. Egeler : I must have a moment for computation.