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.
394
Transactions of S.M.P.E., Vol. XII, No. 34, 1928
small portion of the thickness of motion picture film it greatly increases the brittleness of the film at low humidities. Much of the cracked and torn film returned to the exchanges would not be in evidence if proper humidity conditions could have been maintained for the film while in service.
Percent relative Humidity Fig. 4. Curves showing influence of humidity on the flexibility of film.
In the following discussion it is attempted to point out a source of static charges often encountered in handling film and to show how the proper moisture content of the film provides for the harmless dissipation of the charges. It can be shown with an electrostatic voltmeter that when uncoated cellulose nitrate film moves out of contact with a metal roller it takes on a static charge. If a sheet of gelatin is used in a similar experiment it also takes on a charge, but of opposite sign to the charge on the uncoated film, and of less magnitude. With reference to a roller covered with tin-foil the uncoated film takes a negative charge and the gelatin a positive charge. In positive motion picture film we are confronted with the unfortunate situation of having the two sides composed of materials which easily electrify with charges of opposite sign. When a roll is unwound a cellulose nitrate surface is being separated from intimate contact with a surface composed largely of gelatin. The above experiments indicate that one -side would be charged positively, the other negatively. If the charges are not dissipated