Journal of the Society of Motion Picture and Television Engineers (1950-1954)

Speed, contrast, and graininess in the ultraviolet region of 2650 A, were measured by R. D. B. Fraser in England,227 for 10 motion picture emulsions. The number of photographs which may be obtained for a given radiation dosage is an important characteristic of an emulsion in the ultraviolet cinephotomicrography of living cells. Fraser derived an index useful as a guide to this quantity. Ultraviolet photographic plates introduced in 1949 and described in 1950 by Schoen and Hodge228 are made to be sensitive to the very short ultraviolet wavelengths which can only be photographed in the vacuum spectrograph. The plates depend on having the minimum amount of gelatin covering the silver halide of the emulsion to reduce ultraviolet absorption by gelatin to a minimum. Polaroid -Land film, Type 41, producing black-and-white prints was introduced.2^ Two new nuclear emulsions were developed by Eastman Kodak, the Type NTB2 and the Type NTG3 plates.230 The latter is designed to record lowenergy alpha particles and low-energy protons to 7 mev. Kodak autoradiographic plates, Type A and Type No Screen, for use in radioactive isotope research, were also made available. In addition, a high resolution emulsion for autoradiography was described by Berriman, Herz and Stevens.231 This material consists of a glass support carrying a strippable 10-/i gelatin layer which carries on its upper surface a 4-/tt thickness of fine-grain concentrated emulsion. The characteristics of this emulsion have been investigated and the resolving power measured by making autoradiographs from radioactive test charts producing a value of at least 200 lines/mm. A method of preparing an emulsion for the recording of nuclear particles is described by Demers.232 It is stated that this emulsion is sufficiently sensitive to record electron tracks at energies down to 1.8 times the minimum ionization energy. The spectral sensitivity of Kodak No Screen and Kodak Industrial Type K, X-ray films were determined233 in the region between 0.2 and 2.5 A. Intensification with ozone, producing speed increases from 9 to 1 00%, 234 gold sensitization of X-ray films,235 and a brief review of treatment of under-exposed negatives236 were described in other papers presented in 1950. The combined effect on the latent image of infrared radiation and intensification was investigated by the Eastman Kodak Research Laboratories.237 The use of 6-nitrobenzimidazole and benzatriazole as antifoggants is discussed by Schantz,238 while ion-exchange methods used for the reclamation of wash water were described by Levinos239 of Signal Corps Engineering Laboratory. Double development of nuclear emulsions has been investigated by Jech.240 Uniform development throughout the depth of nuclear emulsions has been difficult to achieve. Stevens241 of Kodak Ltd. has investigated temperature coefficients of swelling and development in 100-M NT1 nuclear plates. Low-intensity reciprocity failure investigations continued, with papers by Katz,242-243 and Webb.244-245 Milne of the Institute of Optics, University of Rochester,24* studied a new reciprocity failure in exposure at high intensity and short duration. For simple blue-sensitive emulsions, the reciprocity law is found to be valid for exposure times somewhat shorter than 10~5 sec. However, in the case of Super XX (dye-sensitized emulsions), a new reciprocity failure is observed for exposure times shorter than 10"6 sec and amounting to 0.2 to 0.3 log units of exposure referred to a density of 1.0, for exposure times of 10~6 sec. Exposures made with the aid of filters indicate that this failure occurs only for that part of the exposure contributed by the sensitizing dyes and does not occur for 472 November 1951 Journal of the SMPTE Vol. 57