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film) gave relative outputs which were in good agreement, a point which helps to establish confidence in the suitability of the films for present purposes. In using magnetic frequency films, individual reproducer azimuth adjustments must necessarily be made until such time as the Society's standard azimuth films become available.
The Westrex film was made on a recorder equipped with facilities for producing an accurately aligned 100-mil sound record and the RCA film was produced under similar conditions with the exception of the sound record which is 200 mils wide. One of these films will be used as the standard frequency film for the Magnetic Reproduce Characteristics Sub-subcommittee's first project, the determination of present differences in reproduce characteristics of the various currently available 1 6mm magnetic projectors. Both films were forwarded to Chairman D'Arcy, who reports that his initial use indicates that they are entirely suitable for the purpose. Rather than circulating the original film, with attendant risk of loss or damage, it appears desirable to make identical copies, checking their individual calibrations against the original. At this writing (March 30, 1953) this work is under way. Every effort is being exerted toward having the secondary standard films in the hands of equipment manufacturers in time to allow reproduce characteristics to be measured and reported for consideration during the forthcoming SMPTE convention.
With satisfactory means for establishing in absolute terms the calibration of magnetic frequency films now available, it be
comes possible to produce a single fre4 quency standard signal-level magnetic tests film, as discussed in Dr. Frayne's addendum to Mr. D'Arcy's paper on standardization* needs. In a recent communication, Mr. D'Arcy points out that the need for such a film is great, and requests that those interested in it communicate with him by* mail or during the Hollywood convention* on the matter of setting up suitable specifications for its production. A standard signal-level magnetic test film is essential in all work leading to the establishment of standards for such reproducer characteristics as reserve gain, dynamic reproduction range, and permissible distortion. It is also essential for calibrating equipment to be used for the evaluation of different types of magnetic sound tracks with respect to optimum bias, coerciveness (sensitivity), and retentivity (aging). Standard signallevel films cannot be produced satisfactorily by employing only controlled recording conditions because of unavoidable variations in these track characteristics, and because it is extremely difficult to maintain over extended periods stable conditions with respect to such factors as head wear and intimacy of head/track contact. As Dr. Frayne states, having standard signal-1level test films for field use individually calibrated in terms of the absolute value of magnetic induction may be neither neces-! sary nor desirable. Mr. D'Arcy feels, however, that all primary standard signal-level and frequency films must be so calibrated if the standardization needs in magnetic recording and reproducing are to be met.
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April 1953 Journal of the SMPTE Vol. 60