Journal of the Society of Motion Picture Engineers ( Volume: 17, Issue: 2, August 1931)

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Straight-Line and Toe Records with the Light-Valve

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Publisher: SMPTE
Doc Type: Journal Article
Abstract: A comparison is made of certain types of sound recording by the variable density method, assuming a light-modulation device which is itself free from distortion. These types are: (1) toe recording where only the toe of the H & D curve is used both for negative and for positive; (2) composite straight-line records where negative exposures are confined to the straight-line portion of the H & D curve, and in printing use is made of a portion of the positive toe, the over-all projected gamma being greater than unity; (3) straight-line recording where both negative and positive exposures are confined to their respective straight-line portions, and the over-all projected gamma equals unity. The analysis shows that, by observing certain requirements, distortionless sound records can be made on all three types. In signal volume the toe record is louder than the composite and the latter louder than the strict straight-line record. In ground noise the toe record is inferior to each of the other two. The signal-to-noise ratio is greatest for the record where only the straight lines are used and least for the toe record. The application of noise reduction to these three records is discussed, and it is shown that, with the same freedom from distortion, a noise reduction of 6 db. may be attained in toe recording, 10 db. in the composite type, and 14 db. in the third type. The fact is emphasized that the pictorial object is not necessarily identical with the acoustic, since pictorially useless toe recording is capable of acoustic excellence. Sensitometric data are discussed, and it is pointed out that in computing the over-all gamma account must be taken of the ratio of negative printing density to negative visual diffuse density, and of the ratio of projected print density to visual diffuse print density, as well as the distinction between intensity scale and time scale sensitometers.
Publication Date: 1931-08-01
DOI: 10.5594/J08011
Link: https://doi.org/10.5594/J08011
Author(s): Donald Mackenzie
Keyword(s): Article

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Donald Mackenzie; Straight-Line and Toe Records with the Light-Valve, Journal of the Society of Motion Picture Engineers ( Volume: 17, Issue: 2, August 1931); SMPTE, 1931. Available at https://doi.org/10.5594/J08011

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Donald Mackenzie; Straight-Line and Toe Records with the Light-Valve, Journal of the Society of Motion Picture Engineers ( Volume: 17, Issue: 2, August 1931); SMPTE, 1931. Available at https://doi.org/10.5594/J08011

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<span class="citation">Donald Mackenzie; <cite>Straight-Line and Toe Records with the Light-Valve</cite>, Journal of the Society of Motion Picture Engineers ( Volume: 17, Issue: 2, August 1931); SMPTE, 1931. Available at <a href="https://doi.org/10.5594/J08011" target="_blank" rel="noopener">https://doi.org/10.5594/J08011</a></span>

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Donald Mackenzie; Straight-Line and Toe Records with the Light-Valve, Journal of the Society of Motion Picture Engineers ( Volume: 17, Issue: 2, August 1931); SMPTE, 1931
doi: 10.5594/J08011
url: https://doi.org/10.5594/J08011

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<li>
Donald Mackenzie; <cite id="bib-10-5594-j08011">Straight-Line and Toe Records with the Light-Valve</cite>, Journal of the Society of Motion Picture Engineers ( Volume: 17, Issue: 2, August 1931); SMPTE, 1931
<span class="doi">10.5594/J08011</span>
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Some Photographic Aspects of Sound Recording [Active]
Analysis and measurement of distortion in variable-density recording [Active]