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318 J. A. MAURER [j. s. M. P. E.
constant-amplitude 16-mm. negatives having densities in the range from 1.0 to 1.7, the print densities covering the same range. The variation of high-frequency output with negative and print densities is too small to be shown on these graphs.
Curve B of Fig. 2 shows the equalization commonly employed in recording 16-mm. sound negatives with white light, while curve C shows the resulting overall characteristic. It has been our experience that films made according to Curve C are more often criticized as "too bright" than as being deficient in high-frequency response in comparison with optically reduced prints. The reason for this will be apparent when we come to consider the characteristics of commercial 16-mm. reproducers.
No curve is given for the response obtained by running the 16-mm. sound negative on a reproducer because it has been found that the relationship between negative and print is not one that can usefully be represented by plotting their individual frequency response curves. Thus, at certain densities the print gives a better frequency response than the negative from which it was made. It is not the light-modulating ability but the contrast of the high-frequency portions of the negative that is important. For this reason "printer loss" can not usefully be expressed in decibels.
Optical printing of 16-mm. negatives appeared likely to offer the advantage of increased effective contrast of the negative, resulting from the collimated nature of the light, together with the possibility of providing for negative shrinkage without encountering the synchronization difficulties of the non-slip type of printer. In order to find out whether or not these advantages could be realized in practice, a printer was built, using a recorder movement at each end of a one-to-one optical system made up of the best available microscope lenses. White-light prints made with this printer gave I1/ \ decibels higher response at 6000 cycles than non-slip prints from the same negatives.
Curves D and E of Fig. 2 show the effect of optical printing from the negatives that gave the non-slip prints represented by Curves A andC.
As may be seen from Fig. 2, films made by direct 16-mm. recording, using standard positive film and white light, and printed by white light, are at least as good from the standpoint of frequency response as prints made by optical reduction. But this is by no means the best that can be done.