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those presented here, but these investigators did not determine the timeintensity curve. They calculated the average intensity from the measured photoactinic effect on film (by comparison with a standard) and from knowledge of the duration determined either by photographing rapidly moving objects of known velocity, or by use of rotatingdrum-camera pictures.
Continuing experimental studies of explosive flashlamps should consider other rare gases such as krypton, neon and xenon as well as other explosives for creating the shock wave. Since xenon is preferred to argon in electronic flashlamps, it is assumed that it might be better in explosive lamps.
Photography With Argon Flashlamp
Consider now the photographic use of the l-jtisec argon flashbulb as described. The following relationship is often useful in arriving at a preliminary set of exposure conditions:
DA =
where
D = lamp-to-subject distance in feet
A = aperture of lens
Q, = total light output in lumenseconds
M = reflector factor
K = a constant which depends upon the type of film used and the processing.
For the argon flashlamp without a reflector, M = 1 and Q, = 10 X cp-sec = 2000 Im-sec (approximately). K is about 0.25 for fast film. Now if A is selected to be about//4.5, then the lampto-subject distance, D, can be calculated. D equals about 5 ft.
This result must be used with judgment, depending upon the reflectivity of the subject that is being photographed. Often a sheet of white cardboard imme
diately back of the subject is very useful in giving a silhouette of darker portions of the subject.
The contrast of photographs is usually low when they are taken with blue light of short exposure time. This lack of contrast can be corrected by a longer development time or the use of a more vigorous developer.
References
1. A. Michel-Levy and H. Muraour, "Photographs of phenomena accompanying explosion of a brisant explosive," Compt. rend., 204: 576-579, 1937.
2. H. Muraour, "Shock waves and detonation luminosities," Chimie & Industrie, 47: 3-15, 1942.
3. H. Muraour, A. Michel-Levy and E. Vassy, "A flash source for photographic purposes," Rev. optique, 20: 161-164, 1942.
4. Safety in Mines Research Board, 25th Annual Report, 1946, H. M. Stationery Office, London, 1947, pp. 29-31.
W. C. F. Shepherd, "Coal mining explosives; present day research of the Safety in Mines Research and Testing Branch, Ministry of Fuel and Power," in Proceedings; Fifth International Conference of Directors of Mine Safety Research, Bull. 489, U.S. Bureau of Mines, U.S. Government Printing Office, Washington, D.C., 1950.
5. J. E. Eldridge, P. M. Fye and R. W. S. Spitzer, "Photography of underwater explosions," Office of Scientific Research and Development, Report 6246, 1947 (P.B. 96667, Office of Technical Services, U.S. Department of Commerce, Washington, D.C., 93 pp.) See also: Paul M. Fye, "The high-speed photography of underwater explosions," Jour. SMPTE, 55: 414-424, Oct. 1950.
6. H. E. Edgerton and C. W. Wyckoff, "A rapid-action shutter with no moving parts," Jour. SMPTE, 56: 398-406, Apr. 1951.
7. H. E. Edgerton, "Light-meter uses with electronic flash," PSA Jour., Part II, Photographic Science and Technique, 16: 6-10, Jan. 1950.
Winning and Edgerton: Explosive Argon Flashlamp
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