No coin nor oath required. For personal study only.
The prospective purchaser of 16 millimeter sound motion picture projectors is often confronted with the preparation of a specification which will insure the purchase of equipment having good performance at reasonable cost. A%ide from performance standards, which should approach 35 mm. performance wherever possible, other factors such as compactness, portability, ruggedness, simplicity, and reliability are important.
It is desirable that specifications be prepared from the viewpoint of objective tests. The overall performance of the complete sound system will indicate, in large measure, the operating characteristics of a projector.
However, at present, certain difficulties and lack of suitable test film prevent direct measurement of some of these characteristics.
In Circular C439 liilbert F. Snyder discusses, in detail, the performance requirements of high-grade 16 mm. sound motion picture projectors.
Suitable test methods are described which can be duplicated by large school systems and other agencies with technical departments.
Particular treatment is given to the overall response-frequency characteristic, signal-to-noise ratio, harmonic distortion, flutter measurement, directional characteristic of loudspeaker, and noise of operating mechanism.
Simplified methods of sound measurement are described.
Results of tests of six representative projectors are included.
Comments are made on the present-day performance of 16 mm. projectors and possible improvements are suggested, ;1 liberal amount of background material has been included and a list of literature references indicates additional source material.
Copies of C439 are obtainable from the Superintendent of Documents, Government Printing Office, IVashington, D. C., at 15 cents each.
The tendency toward the more extensive use angle photographic objectives in airplane mapping of wide cameras
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Mar., I95o. 1 ## BOOK NOTES 26I new edition such topics as nuclear transformations and their applications, silicates and their structure, high polymers, fluorine compounds, and ion exchangers have been expanded.