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1949
REPRODUCING CHARACTERISTIC
393
and, 16-mm projectors incorporating 35-mm features demonstrate that much better 16-mm work will be done in the future. Optical slits, giving an effective scanning height of 0.6 to 0.7 of a mil, are now being employed. This means that response can be obtained up to 5000 cycles without excessive equalization. It seems logical and practical to have the electrical characteristic for 16-mm reproduction follow very closely that of 35-mm up to 5000 cycles. Low-pass filters can then be installed at 5000 or 6000 cycles, depending upon the nature of the material and application. As was considered on the 35-mm characteristic, the loudspeaker system must be taken into consideration when evaluating the final reproduction curve.
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Fig. 2 — Approximate re-recording characteristics; 35-mm release sound track for 16-mm release.
Fig. 3 shows the recommended optimum response which is easily obtained with simple networks, and the dotted line shows the ideal characteristic that is desirable. In portable equipment it naturally follows that the characteristic must be balanced around a geometric mean3 of 800 cycles. It is not advisable to extend the high-frequency end when the loudspeaker enclosure will not maintain a balance at the low end. Where larger two-way systems are to be used, and are the equivalent of that being used in 35-mm, the over-all characteristic can approximate the 35-mm characteristic over a range of approximately 80 to 6000 cycles.
The Navy has recently indicated that all of their future planning for mobile or portable motion picture presentation will use only 16mm release. As a result of this large single user, it seems desirable