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.
W FUNDAMENTALS There is no apparent change in the emulsion, but on being im- mersed in a developer, an image or picture is produced. This is in a negative form in which the objects which were black in the original are white, and those which were white are black. More light is reflected from the light-colored sections of the scene and, therefore, more chemical action takes place in the corresponding section of the film. When this is developed, silver is deposited in the dark areas, and in the lighter areas where there was no light, the undeposited silver is washed away. Before the film so made can be used, it is necessary to reverse it, thus making a positive which has the same colors and shades of light as the original. This can be done in two ways. One method is by direct reversal in which the film which was in the camera, known as a reversal film, is chemically treated a second time. This treat- ment literally reverses the colors of the film, and parts which were white become black, and those which were black become white. The film then has the same color-shade values as the original scene, and is known as a direct-reversal positive. In the other, and more generally used system, the negative is photographed onto another film. In exactly the same manner in which the color values were reversed when the negative was made, so are the colors again re- versed on the second film. By virture of this double reversing, the second film becomes a positive which is then used for projection or televising. It will be seen that the former method suffers from the drawback that only one film exists, and if anything happens to it there is no way of replacing it. There are many different types of film stock available. The various manufacturers have their own trade names for them, but film emulsions fall into certain well-defined categories. Negative and positive stocks have already been mentioned. In this case, the difference in the raw (unexposed) film is in the speed and fineness of grain. Emulsion speed is the main difference between the differ- ent types. By emulsion speed is meant the sensitivity of the emulsion to light and the speed with which a picture is formed on the film. Modern chemistry has achieved a great deal in preparing fast emul- sions, but unfortunately as the speed of the film increases another