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476 JENNINGS, STANTON AND WEISS
Volume output of both magenta and sulfided sound tracks is normal, being within 1 or 2 db of a standard silver track. Signal-tonoise ratio is somewhat better than black-and-white positive, attributable to the exceedingly fine grain structure of the colored image. Following are typical signal-to-noise ratios comparing the three types of track for variable-area recording without noise reduction:
Fine-grain Release Positive (black-and-white) 36 db;
Type 275 magenta track (IP 37 cell) 38 db;
Type 275 sulfide track (868 cell) 40 db.
High-frequency reproduction with color sound tracks is somewhat inferior to silver tracks. This is particularly true of sulfided tracks. The loss is caused partly by the high negative track density requirement and partly by the fact that a sulfided track utilizes all three of the emulsion layers of the color film. At«9000 cycles a magenta variable-area track is about — 2 db from a silver track, while the sulfided track is about — 7 db from the silver reference. Some highfrequency boost during recording may be necessary with the latter combination.
ACKNOWLEDGMENT
The developments reported in this paper were made possible through the combined efforts of many Du Pont research workers. In addition to the work in the laboratories of the Technical Division, Photo Products Dept., Parlin, N.J., extensive contributions have been made by the Chemical Department, Experimental Station, Wilmington, Del.
REFERENCES
1. R. Fischer, German Patent No. 253,335, 1912.
2. R. Fischer and H. Siegrist, "The formation of dyestuffs by means of oxidation
with irradiated silver halides," Phot. Korr., vol. 51, pp. 18-21, 1914; pp. 208211, 1914.
3. C. E. K. Mees, The Theory of the Photographic Process, p. 59, Macmillan, New
York, 1942.
4. R. Gorisch and P. Gorlich, "Reproduction of color film sound records," Jour.
SMPE, vol. 43, pp. 206-213, September 1944.
5. A. M. Glover and A. R. Moore, "A phototube for dye image sound track,"
Jour. SMPE, vol. 46, pp. 379-386, May 1946.
6. R. D. Drew and S. W. Johnson, "Preliminary sound recording tests with
variable-area sound tracks," Jour. SMPE, vol. 46, pp. 387-404, May 1946.