High Speed Photography

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High speed photography is the science of taking pictures of very fast phenomena. In 1948, the Society of Motion Picture and Television Engineers defined high-speed photography as any set of photographs captured by a camera capable of 128 frames per second or greater, and of at least three consecutive frames. High speed photography can be considered to be the opposite of time-lapse photography. In common usage, high speed photography may refer to either or both of the following meanings. The first is that the photograph itself may be taken in a way as to appear to freeze the motion, especially to reduce motion blur. The second is that a series of photographs may be taken at a high sampling frequency or frame rate. The first requires a sensor with good sensitivity and either a very good shuttering system or a very fast strobe light. The second requires some means of capturing successive frames, either with a mechanical device or by moving data off electronic sensors very quickly. As film and mechanical transports improved, the high-speed film camera became available for scientific research. Kodak eventually shifted its film from acetate base to Estar (Kodak's name for a Mylar-equivalent plastic), which enhanced the strength and allowed it to be pulled faster. The Estar was also more stable than acetate allowing more accurate measurement, and it was not as prone to fire. Each film type is available in many load sizes. These may be cut down and placed in magazines for easier loading. A 1,200-foot (370 m) magazine is typically the longest available for the 35 mm and 70 mm cameras. A 400-foot (120 m) magazine is typical for 16 mm cameras, though 1,000-foot (300 m) magazines are available. The rotary prism camera allowed higher frame rates without placing as much stress on the film or transport mechanism. The film moves smoothly past a rotating prism which is synchronized to the main film sprocket. Each revolution of the prism paints the same number of frames onto the film as there are faces on the prism. A shutter also improves the results by only opening as the prism faces are nearly parallel, and then closing again. Redlake Hycam and Fastax cameras are capable of 10,000 frame/s with a full frame prism (4 facets), 20,000 frame/s with a half-frame kit, and 40,000 frame/s with a quarter-frame kit. [READ THE REST OF THIS ARTICLE]





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