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The variety, range and precision of methods available for photographic recording of fast phenomena have been increasing steadily. The capabilities of some of the newer techniques will be described. At the lower end of the speed range, the advances have been mainly in improvements in resolution, and in the introduction of video techniques. At the highest speeds the advances have included increases in dynamic range, a wider acceptance of image tubes, and a more careful analysis and characterization of their limitations. The variety, range and precision of methods available for photographic recording of fast phenomena have been increasing steadily. The capabilities of the newer techniques are considered, classifying the methods by the kind of record obtained. Descriptions of experimental techniques and apparatus, and illustrations, are given in an earlier article entitled, "A Review of the Methods of High-Speed Photography," published in Reports on Progress in Physics in 1957;[1 and in "Advances in High Speed Photography 1957-1972" published in the Proceedings of the Tenth Internatiopal Cngress on High Speed Photography (HSP10) [116 and also in JSMPTE 82 167-175 (1973). L117o This present paper is in the nature of a survey of the limits to which the various techniques have been pressed as compared to the limits attained, or reported in the open literature, at the date of the reviews 10 and 25 years ago. There are a number of recent books and articles which also provide excellent surveys and impressive bibliographies:129 -138 Streak records with drum cameras can give a time resolution of 5 x 10-9 s.[2,3] Rotating mirror streak cameras with a single reflection[15] at present approach 10-9 s and may with multiple reflections achieve 10-10 s. The Schardin limit[ 4] for presently available rotor materials is 0.25 x 10-9 s, but this is predicated upon a single reflection of the light beam from the rotor and can be surpassed if the camera is designed to take advantage of multiple reflections. Deflecting image converters go much further: 5 x 10-13 s [5-12,115,125,139-13] (see Table I). There has been a notable increase in the last ten years in the use of image converter tube cameras of many kinds particularly for the study of laser pulse structure and for investigations of electrical breakdown. Deflecting image converter tube cameras are now also being used for studies at UV and shorter wavelenghts - though the time resolution is somewhat longer than for visible light studies.[123] Twenty-five percent of all papers presented at recent HSP Congresses involve ICTs. Single flashes of light, bright enough for silhouette recording, can be as short as 3 x 10-14 s[118,137,138I and similarly short for reflected-light recording for small near objects, or 10-12 s for a field of view a meter square or more. The very short flashes just mentioned are laser flashes. The availability in many labs of picosecond laser pulses is one of the significant advances of the decade. The power in the laser flash can be very high, but it should be noted that the integrated energy in the flash is always less than the energy in the flashlamps or primary lasers that pump the laser. There has been a steady advance in the design of open sparks and of gas discharge tubes and associated equipment, though this light output is rarely briefer than N/107 where N is the stored energy in joules. [16-26,129-131] Electrically driven Kerr cells can operate with an exposurc of 5 x 10-10 s. Optically driven Kerr cells can give exposures of a few picoseconds.[32) Simple image converter tubes can work at 10-10 s and with greater light transmission than Kerr cells.[7,30,311
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