Living pictures; their history, photoproduction and practical workingWith a digest of British patents and annotated bibliography . Fig. J42. PRESENT-DAY APPARATUS. 121> continually pulling at the film, and at the end of anexposure the film lies in a straight line between themand the pressure-frame. An interposed disc bears aneccentric rod, which strikes the film once in a revolutionand draws some film down. It will beseen that for a fixed position of thedisc the amount of film drawn on willdepend on the distance over which thedog travels in contact with the film,and this is adjustable by sh
Living pictures; their history, photoproduction and practical workingWith a digest of British patents and annotated bibliography . Fig. J42. PRESENT-DAY APPARATUS. 121> continually pulling at the film, and at the end of anexposure the film lies in a straight line between themand the pressure-frame. An interposed disc bears aneccentric rod, which strikes the film once in a revolutionand draws some film down. It will beseen that for a fixed position of thedisc the amount of film drawn on willdepend on the distance over which thedog travels in contact with the film,and this is adjustable by shifting thedog along a slot on the disc. On theother hand, the relation between theperiods during which the film ismoving and stationary is governed \:iythe number of degrees ( the propor-tion of a revolution) during which thedog touches the film. If, therefore, thedisc be made larger and its centre removed to a greaterdistance from the film, the dog will bring down an equalquantity of film in a less time, leaving the film stationaryfor a longer Fig. 143. D2. Film moved intermittently by reciprocated roller, etc. The roller which strikes the film need not have arotary action, though that is perhaps the best form,there being no dead point. Evans in 1890 showed adouble tilting-arm applied to this purpose (see Figs. 71and 72), while Varley almost simultaneously invented acam-reciprocated arm (Fig. 73). Both these actionstook place over an arc ; but Fig. 144 shows a crank-roddriving a roller in a line at right angles in order to loopthe film. Blair has suggested a machine having a rise-and-fall shutter instead of one according to the ordinarytype; and his drawings show the roller placed on top of K
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Keywords: ., bookcentury1800, bookdecade1890, booki, booksubjectmotionpictures
