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.
142 MOTION PICTURE HANDBOOK
Table 1 is what might be termed the "angle table." It represents the tabulated results of what is shown in the diagram in Fig. 4. In order to apply this table proceed as follows:
First measure the diameter of the opening of the objective lens. Next, with the picture in exact focus on the screen, stick a rule through the aperture of the machine and place it against the back surface of the back combination of the objective lens, and measure the exact distance from the lens to the film, or, in other words, from the lens to the surface of the film track on the aperture. This will give you the exact back focus of the lens at the position in which it works. This is of the greatest importance because any given lens may work in different positions under different circumstances. Having found the measurement of the diameter of your objective, and its back focus when in working position, proceed as follows :
In the extreme right-hand column find the number most nearly corresponding1 to the back focus at which your lens is working. Opposite this number, in the extreme left-hand column you will find the smallest lens diameter permissible at that back focus, and at the top of the right-hand column we see that the condensers must be two "7%s," with 22 inches between the apex of the front lens and the film. For example: Suppose the B. P. to be 4% and the-* lens diameter 1% inches. At the sixteenth line down we find 4.52 (practically 4%) in the righthand column, and opposite, in the left-hand column, 1%. We therefore see that 1% is the least permissible lens diameter, and that our lens is unsuitable to the work in hand. Looking at the top of the righthand ^column we see that with the 1%-inch lens we must have two 7% condensing lenses with not less than 22 inches between the apex of the front lens and the film. This is the extreme condition. Looking in the third column from the right, however, one line further down we again find 4.52 and discover that with a lens 1 15/16 inches in diameter we may use two inches less between condenser and film, though two 7% lenses are still required. Again looking, we find 4.60 in the fourth, 4.6 in the fifth and so on over to the twelfth column, where we find 4.540 In the bottom row and see that with a lens 3 inches in diameter we could use one 5% and one 6% condenser, with 11 inches from apex of front lens to film — the extreme condition in the other direction.
Table 2 shows relative distances of conjugate foci and amount of enlargement of the image of the object, the object being the crater or source of light and the image the spot on the aperture.
Diagram A, Plate 13, shows the points from which the distances are measured with piano convex combinations.
Diagram B, Plate 13, shows the points from which the distances are measured with a meniscus-bi-convex combination. With the piano convex combination X equals the distance from the crater 'to the curved surface of the back condenser,