The direct source of light which in the author’s laboratory has produced
the most perfect photographic effects, i. e., photographs absolutely
without lines, consists of a lamp about an inch in diameter and two
inches long, fitted with a standard screw base. The tube contains a .6
mil filament with a small single turn coil in a hydrogen atmosphere.
The coil is offset until it almost touches the glass wall. Such location
of the coiled filament permits the effective placing of a minute
aperture in very close relation to the filament; whereas an aperture on
the outside of a bulb with the light source in the centre of the bulb
acts like a pin-hole camera, and sharpness of image is practically
impossible (unless a lens is used).
The lamp described above will respond to fluctuations in current well
above a thousand times per second, but requires voltages about four
times normal. It was made for the author by courtesy of the General
Electric Company, under the direction of Mr. L. C. Porter, of Harrison,
N. J.