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.
136
MOTION PICTURE HANDBOOK
the objective lens. Always bear in mind one fact, viz.: the optical action of the objective lens and the optical action of the condensing lens is in every respect identical.
Now to follow this matter through we will consider Plate 17, which is a photographic representation of light ray action in an objective lens, in which X is a shield containing a standard machine aperture, covered by a brass plate containing two pinholes. Y is a standard projection lens, with onehalf of its barrel cut away, 1 and 2 being respectively the back and front factors of the lens, though 2 is hidden behind its container. This photograph is made with the aperture and the lens in actually working position, and with the light projected through the condenser in the ordinary way, under actual operating conditions. You will observe that the light coming through the upper pinhole, Plate 17, diverges into a cone, which corresponds to cone A, 1-2, Plate 14. This cone covers very nearly the full aperture of the lens. The light passing through the lower pinhole does exactly the same thing, and the two cones begin to intermingle at L, and from there on to the lens a small central light pyramid is shown, the upper half of which is the upper edge of the lower pinhole cone, and its lower edge the lower edge of the upper pinhole cone. Beyond the back factor of the lens, between the two lens factors, you can easily trace the action. And it is made clear in this photograph that the bend which starts the final crossing or transposition of the rays takes place at the
first or back surface of the first or back combination of the objective, even as it takes place at the back surface of the rear lens, Plate 14. The action, as between the diagram, Plate