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1949 LEAD-SULFIDE PHOTOCONDUCTIVE CELLS 703
(4) The possibility of a simplified exciter-lamp power supply, or even operation of the lamp directly from the alternating-current line.
(5) Stability and long life for any given cell. Some possible disadvantages:
(1) Reduced signal-to-film -noise ratio from all types of dye sound tracks now available.
(2) Greater variations from cell to cell, particularly as regards sensitivity, than with present production of photoemissive cells. Selected cells may be available, however,
(3) A high-frequency response curve which is not quite as good as that of gas photoemissive tubes.
The poor behavior with presently available dye track is potentially the most serious of these disadvantages; its real seriousness can only be measured when the commercial intentions of the film companies with regard to the use of this track become better defined than they are at present.
ACKNOWLEDGMENT
I wish to express my thanks to Mr. S. Hayes and Mr. R. J. Schreiner of this Laboratory, who took most of the data presented here, and my appreciation to Dr. F. B. Berger for many valuable discussions on the subject.
REFERENCES
«(1) R« J Cashman, "Lead-sulfide photoconductive cells for sound reproduction," /. Soc. Mot. Pict. Eng., vol. 49, pp. 342-348; October, 1947.
(2) Norman Anderson and Serge Pakswer, "Comparison of lead-sulfide photoconductive cells with photoemissive tubes," J. Soc. Mot. Pict. Eng., vol. 52, pp. 41-48; January, 1949.
(3) P. Vlahos, "Lead sulphide phototubes," Mot. Pict. Res. Council, September 24, 1948.
(4) Alan M. Glover and Arnold R. Moore, "A phototube for dye image sound track," J. Soc. Mot. Pict. Eng., vol. 46, pp. 379-386; May, 1946.
(5) Private communication to the author.
(6) R. Gorisch and P. Gorlich, "Reproduction of color film sound records," /. Soc. Mot. Pict. Eng., vol. 43, pp. 206-213; September, 1944.
(7) R. O. Drew and S. W. Johnson, "Preliminary sound recording tests with variable-area dye tracks," /. Soc. Mot. Pict. Eng., vol. 46, pp. 387-403; May, 1946.
DISCUSSION
MR. J. A. MAURER: If I understood you correctly, you stated that the response is not so much proportional to the total amount of light striking the cell as it is to the average intensity of the light striking the cell.
MR. RICHARD W. LEE: That is correct. If you have a given total amount of