Cinematographic annual : 1930 (1930)

440 CINEMATOGRAPHIC ANNUAL value, not primarily as a check on the recording but rather as a check on the performance which has been recorded. Many directors rely to a large extent on playbacks, while others take little interest in them. Although their true value in aiding production cannot be accurately estimated at present, playbacks will certainly find a place of much importance in the ultimate scheme. FIGURE 7 Magnified Cross-Section of Grooves in a Wax Record Having completed the recording of a scene which the director has approved after hearing one wax played back, the other wax record or records go through additional processes which correspond generally with the film development and printing. After suitable preparation, the wax record is immersed in an electroplating bath by means of which a heavy layer of copper is deposited on the surface of the soft wax. This copper layer or shell, when separated from the wax, constitutes an exact copy of the original recording, except that it is negative in character, bearing ridges where the original record bore grooves. This difference is illustrated in Fig. 7 , where the black portion represents a crosssection of an original wax and hence the white portion may be taken to represent the copper shell which has been obtained from the original. This shell is called a matrix, or sometimes a master negative, and is used to make a few of the familiar black pressings or finished records. In the case of original recordings these records may be used for re-recording, whether preliminary or final, and in the case of final recording they are used in testing the quality of the recording and of the production. For studio uses, therefore, the additional processes corresponding to the printing and developing of a positive film are not necessary, a fact which results in further savings of many thousands of dollars annually.