Abstract
FOR some time past, photographic materials sensitive to radiation between 7000 A. and 9000 A. have been available. The sensitivity of these plates has, however, not been high. The Ilford Company has now produced a plate which possesses a comparatively high sensitivity for this region of the spectrum. With a subject illuminated by two 1500-watt gas-filled lamps at a distance of about eight feet and screened by filters cutting off radiation of shorter wave-length than 7000 A., the exposure is about half a second with the lens working at f. 4. Such photographs, taken in the dark, serve as an excellent demonstration of the existence of invisible radiation; the public, already accustomed to the idea of ultra-violet rays, thus becomes familiar with the infra-red. The practical use of these plates is, however, considerably greater than that of demonstrating the actinic power of the infra-red: in astronomical and geographical recording, their power to respond to the unscattered radiation coming through mist and haze from very distant objects makes them particularly valuable.
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New Emulsion Sensitive to the Infra-red. Nature 129, 500 (1932). https://doi.org/10.1038/129500d0
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DOI: https://doi.org/10.1038/129500d0