Exhibitors Herald and Moving Picture World (Apr-Jun 1930)

April 26, 1930 EXHIBITORS HERALD-WORLD 37 »EEH Fig. 5 Synchronizing amplified the power of this current modulates a light to which film is exposed. The resultant latent image is treated chemically and when developed, again modulates a light to produce the positive. After development this positive, when run through a projector, modulates a beam of light, thereby controlling a minute electric current. After amplification the resultant power is sufficient to impart mechanical motion to a loud speaker diaphragm, thereby producing a very close approximation to the original sound. Beginning as sound, fourteen changes of condition must be passed through before the sound is reformed. The same number of changes occur in recording on disc. The changes in condition in the recording process are as follows: Film 0 1 2 3 4 5 6 7 8 Sound Mech. Motion Small Current Large Current Mod. Light Latent Image Metallic Image Mod. Light Latent Image Disc 0 1 2 3 4 5 6 7 8 Sound Mech. Motion Small Current Large Current Mech. Motion Soft Wax Master Mother Stamper 9 Metallic Image 9 Hard Wax 111 Mod. Light 10 Mech. Motion 11 Small Current 1 1 Small Current 12 Large Current 12 Large Current 13 Mech. Motion 13 Mech. Motion 14 Sound 14 Sound Film 0 Sound 1 Mech. Motion 2 Small Current 3 Large Current 4 Mod. Light 5 Latent Image 6 Metallic Image 7 Mod. Light 8 Latent Image Disc 0 Sound 1 Mech. Motion 2 Small Current 3 Large Current 4 Mech. Motion 5 Soft Wax 6 Mother 7 Hard Wax 8 Small Current 9 Metallic Image 9 Large Current 10 Mod. Light 10 Mixing 11 Small Current 11 Large Current 12 Large Current 12 Mech. Motion 13 Mixing 13 Soft Wax 14 Large Current 14 Master 15 Mod. Light 15 Mother 16 Latent Image 16 Stamper 17 Metallic Image 17 Hard 18 Mod. Light 18 Mech. Motion 19 Latent Image 19 Small Current 20 Metallic Image 20 Large Current 21 Mod. Light 21 Mech. Motion 22 Small Current 22 Sound 23 Large Current 24 Mech. Motion 25 Sound DUHjiNC ROOM It was found desirable to arrange the amplifiers in the reproducing circuit so as to reduce mechanical vibration to a minimum. Special amplifiers were built to meet the requirements of re-recording w'ork. It was also necessary to carefully guard against noise being introduced by circulating currents and foreign potentials. The process of recording is such that there When sound is re-recorded there is no intermediate sound step, the energy representing the sound being dealt with in the electrical state. From the standpoint of the changes involved, synchronizing and re-recording are similar, as shown on Figures 5 and 6. These latter processes involve 25 changes of condition when re-recording from film to film and 22 changes of condition from disc to disc. The changes in condition in the re-recording process are as follow's: TRACK 3 TRACK Fig. 8 is a tendency for the high frequencies to be relatively under emphasized. This tendency is not objectionable in the original recording, but becomes undesirable in successive recordings, since it is cumulative. Fortunately, it is possible to do almost anything desired with the frequency response of the electrical portion of the system, hence it was only necessary to design an equalizer to counteract the over emphasis of the low frequencies. Due to the variation of different records, the equalizer was made adjustable. Photographs illustrating dubbed sound tracks are given on Figure 8. The process of dubbing two separate records together is illustrated by track 4, which was produced by combining tracks 3 and 5. The original tracks, 3 and 5, are single frequencies. A re-recording composed of speech and music is illustrated in track 7, being the combination of tracks 6 and 8. From an analysis of track 7, its component parts could be shown to consist cf tracks 6 and 8, although with such complex sounds it is not as apparent to the eye as the dubbed track composed of tw'o different sine waves illustrated in track 4. Track number 1 has been combined from two separate records of music and dialogue. This record was then re-recorded four times, track number 2 in the picture being the fifth successive re-recording. It will be noticed that successive re-recordings tend to diminish resolution, which of course affects quality. The processes outlined are in a stage of development ; consequently the space allotted to this equipment and the type of layouts in the various studios are by no means uniform. It may readily be appreciated that in scoring a picture, the standard recording channel can be used as the pickup is by microphone, as in regular picture production, and the mixing is essentially the same. This also holds for the synchronizing operation such as adding sound effects to a completed picture. In the case of re-recording, it is desirable to adjust the volume of the output of the disc and film reproducers so that it may readily be mixed with musical accompaniment and sequences, and thence put through the regular channel. Due to the threefold function of dubbing, it is, of course, desirable to provide for utmost flexibility in the wiring scheme, as indicated to some extent in Figure 7. This, of course, applies to the signaling and motor system, as well as the transmission circuits. Edited and revised for the Technical Digest of the Academy of Motion Picture Arts and Sciences, from a paper presented before the Society of Motion Picture Engineers, New York City, May 6-9, 1929. Cuts and type courtesy of American Cinematographer. This is the tenth paper in the series. =>-s— ^ Fig. 6 Re-Recording Fig. 7