雅思閱讀真題練習(xí)

　　The introduction of the dry plate process brought with it many advantages. Not only was it much more convenient, so that the photographer no longer needed to prepare his material in advance, but its much greater sensitivity made possible a new generation of cameras. Instantaneous exposures had been possible before, but only with some difficulty and with special equipment and conditions. Now, exposures short enough to permit the camera to the held in the hand were easily achieved. As well as fitting shutters and viewfinders to their conventional stand cameras, manufacturers began to construct smaller cameras in tended specifically for hand use.

　　One of the first designs to be published was Thomas Bolas s Detective camera of 1881. Externally a plain box, quite unlike the folding bellows camera typical of the period, it could be used unobtrusively. The name caught on, and for the next decade or so almost all hand cameral were called  Detectives, Many. of the new designs in the 1880s were for magazine cameras, in which a number of dry plates could be pre-loaded and changed one after another following exposure. Although much more convenient than stand cameras, still used by most serious workers, magazine plate cameras were heavy, and required access to a darkroom for loading and processing the plates. This was all changed by a young American bank clerk turned photographic manufacturer, George Eastman, from Rochester, New York.

　　Eastman had begun to manufacture gelatine dry plates in 1880. being one of the first to do so in America. He soon looked for ways of simplifying photography, believing that many people were put off by the complication and messiness. His first step was to develop, wih the camera manufacturer William H. Walker, a holder for a long roll of paper negative film. This could be fitted to a standard plate camera and up to forty-eight exposures made before reloading. The combined weight of the paper roll and the holder was far less than the same number of glass plates in their ling-tight wooden holders. Although roll-holders had been made as early as the 1850s, none had been very successful be cause of the limitations of the photographic materials then available. Eastmans rollable paper film was sensitive and gave negatives of good quality; the Eastman-Walker roll-holder was a great success.