Democratic Sentinel, Volume 19, Number 20, Rensselaer, Jasper County, 24 May 1895 — Photography by Phosphorescence [ARTICLE]

Photography by Phosphorescence

In the field of lighting by phosphorescence we reach hitherto untrodden ground. Phospherescent light has been associated with the idea of “cold light,” or the property of becoming luminous with the omission of the intermediate step of combustion, is commonly understood. As a physical action, we know it in thelight of the firefly, which Prof. S. P. Langley rates at an efficiency of 100 per cent, all its i radiations lying within the limits the visible spectrum. By means ofSfhe Teslaic currents phosphorescent light stroug enough even to photograph by has been obtained; and a picture, representing the inventor himself, is the first portrait or photograph of any kind ever taken by phosphorescent light. A bulb whose light-giving member is coated with sulphide of zinc treated in a special way was rendered phosphorescent by means of current obtained from a high-frequency transformer coil. The current used was alternated or oscillated about 10,000 times per second. The exposure was about eight minutes. In order to test more closely the actinic value of phosphorescent light, some bulbs subject to high-frequency currents were photographed, or, if we may coin, a new word, “phospliograplied,’’ with a somewhat longer exposure. One bright pair illustrated utilize sulphide of zinc 1 in some form for luminosity. The third bulb, seen faintly to the left of them, has a coating of sulphide of calcium. Although, judged by the eye, it glowed with a brightness fully equal to that of the other two, the actinic value was evidently much less. It is, perhaps, needless to say that these demonstrations invite to an endless variety of experiments, in whiAh inventors will find a host of novel phenomena awaiting them as to phosphorescence and fluorescence produced with electrical currents.—The Century.