We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
Feb., 1930] CHARACTERISTICS OF SOUND FILM 183
proportional to those existing in the set. By means of a lens an image of the object in question is formed on the photographic material. The exposure time for all points on the negative area is the same and hence the distribution of brightnesses existing in the object produces a corresponding distribution of exposure at various points on the negative surface which are directly proportional to the brightnesses existing in the object. In the case of sound recording an analogous situation occurs since the light valve or "flashing lamp" subjects the negative to a series of variable exposures. In the case of picture records and sound records the desirable condition from this point on is a reproduction in the positive of transmission values which are directly proportional to the exposure values incident upon the negative record.
The theory of tone reproduction, applying particularly to general photographic work, has been treated at length in previous publications and the general laws and relationships derived can be applied with certain modifications in details, which may be desirable for the sake of convenience, to the general problem of photographic sound reproduction. For instance, it has been shown that for perfect reproduction of brightness relationships, the product of the negative gamma (TW) by the positive gamma (7^) should be equal to unity, assuming that only the straight line portions of each of the characteristic curves are used. This law is of equal validity in the case of sound reproduction by the variable density method.
In the case of sound on film, the positive sound record must be developed along with the picture positive and hence must necessarily receive the same development treatment, thus being developed to the same contrast (7) as that required to give the desired picture quality. The present predominant practice in the making of motion pictures involves the use of a picture negative developed to a relatively low gamma (0.5 to 0.6), thus requiring for the fulfillment of the above relationship that the positive be developed to a relatively high gamma (1.8 to 2.2). A fair approximation to practice is represented by the following figures:
Tw = 0.55 7p = 2.00 7«.7> = 1.10 = 7r
t will be noted that the product of these negative and positive gammas is slightly greater than unity. It has been found that this is