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.
414
PRINCIPLES OF CINEMATOGRAPHY
l-OO
LOG EXPOSURE
Fig 170. — Characteristics of positive film emulsions.
form intensity. Since positive film can be readily handled in short lengths it is also a relatively easy matter to use the camera as a printing machine and to produce a negative copy from the original positive title. Assuming the original title card carried black letters on a white ground, the original camera film will contain white letters upon a black ground and, after a print has been made from this film, a copy with letters and background similar to the original title card can be produced. This copy may then be threaded in the camera infront of a length of normal reversal film so that titles with a moving pictorial background may be produced. This process is naturally rather lengthy and should only be used when the camera is not fitted with a matte box (see Chapter 12). When matte boxes are available a similar result may be obtained by mounting a section of clear celluloid in front of the camera and upon which black lettered titles may be written.
Some idea of the contrast which may be obtained with positive film is gained from Figure 170. This diagram shows four values of gamma which may be produced with such a film when developed in Kodak formula D-16 for 3-0, 4-0, 5-5 and 8-0 minutes respectively. Obviously, these curves can do no more than indicate the general range of contrast which is obtainable under known conditions. In practice the actual contrast obtained will depend upon several factors such as the age of the developer, the temperature at which it is used, the degree of agitation given to the solution and the type of development which is employed. This last point is mentioned to draw a distinction between machine, tank or dish processing, each of which will produce a slightly different result from the others.