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PRINCIPLES OF CINEMATOGRAPHY
points will be shown by selecting several improvements made in the following branches of cinematography: (1) Improvements in sound recording and reproduction. (2) Improvements in presentation. (3) Animation and trick effects. (4) Special equipments and processes.
(1) Improvements in Sound Recording and Reproduction
(a) Centering Scanning beams by Buzz-Track Control. One of the simplest and yet most helpful recent variations of the photographic sound record is seen in Figure 171. A specially prepared track is used to adjust the position of the scanning beam in the reproducing heads and to indicate in which direction the adjustment should be made. Considering firstly the 35-mm case, shown on the left of the figure, the Society of Motion Picture Engineers have recommended that the width of the scanned area shall be 0 • 084-inch (2 • 144-mm), and that the distance measured from the guided film edge to the track centre shall be 0 • 243inch (6 • 272-mm). The control track suitable for adjusting the reproducer to these dimensions is seen below the film sample at position 'A'. The clear area, 0088-inch (2-235-mm) in width and having its centre 0-243 -inch (6 -272-mm) from the guided film edge, represents the dimensions of the scanned area of a perfectly printed track, plus a clearance of 0002-inch (0 050-mm) on each side. This clearance is provided to accommodate film weave and printing tolerances. A 300 cycle constant frequency note is recorded on one side of this clear area and a 1 ,000 cycle note is recorded on the other side. When such a track is passed through a reproducer a signal will only be heard if the scanning area is misplaced with respect to the film. The nature of the signal will, of course, indicate the direction in which the guide shoes in the scanning gate should be moved in order to correct such misplace
WIDTH OF SCANNED AREA -0084'
WIDTH Of SCANNED AREA ^O Q74'
300 CYCLES/ SEC
OOO CYCLES/SEC
300i
Fig. 171.— Scanning areas centred by "buzz track" control system.