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.
The Carbon Arc
The condition of the arc is denned below each picture. It will be seen that the point of maximum efficiency is just below the maximum current-carrying capacity of the carbons, or in other words, around 18 to 20 amperes.
The foregoing limitations apply, as has been stated, to regular low intensity carbon trims. The use of National SRA Projector Carbons in the low intensity reflector arc lamp permits operation at higher currents than those recommended for regular, low intensity trims. This subject is discussed in detail in Chapter VII.
The relation of carbon diameter and amperage to quantity and quality of light is of great importance to the projectionist. Although, on a carbon of given diameter, crater area continues to increase with current, there is a point, as indicated in the test just described, beyond which it is not practicable to go. For each diameter and type of carbon there is a relatively narrow range of current within which optimum results are obtained and satisfactory operation will only be secured when the arc current is held within the recommended range. These recommended current values have been determined by careful tests in the theatre as well as in the laboratory. They are presented in subsequent chapters where the operation of the various types of projector lamps is discussed.
Here and there is found a projectionist who uses a trim of larger diameter than recommended in order to save trimming or to cut carbon cost. By so doing he sacrifices quantity, quality and steadiness of light. Compared with other expenses in a theatre, the cost of carbons is negligible — only a few cents a day. The product which the theatre sells to its audience is the picture on the screen. A high-priced film, poorly lighted, loses its effectiveness with resultant loss of patronage. It is sound economy.
21