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.
Jan., 1939] UNDERSEA CINEMATOGRAPHY 5
Diving bells and baby submarines were considered, but after talking with a few persons who had had experience with such equipment, we saw that they could not be transported and put into position with sufficient ease and speed to suit the underwater photographer, and they are the plaything of every wave or squall of wind. We attached cameras to water telescopes; we shot them through glassbottomed buckets; we submerged them and sighted through periscopes. But pictures from an unsteady base are unattractive and tend to make the audience seasick. It is our opinion, therefore, that underwater pictures can best be made from the bottom and not the surface ; also, that a compact underwater camera operated by a diver should be used for all picture work in the open sea, lakes, and rivers. The same applies to a considerable degree also in swimming pools and tanks, for the cameraman shooting through a port-hole is greatly hampered in following a moving object, and most underwater subjects depend on action rather than expression to tell their story.
The physical qualities of water are responsible for many of the difficulties encountered in underwater photography. The purest of water is far less transparent than air; and, because it is an excellent solvent, it is rarely pure in nature; and dissolved matter profoundly affects the optical properties. Then, too, water, having greater density and viscosity than air, supports a much greater proportion of suspended matter both organic and inorganic, and this has an even greater effect on its optical properties. The quantity and kind of dissolved matter are relatively constant for any location and, at least in sea water, are nearly the same for almost all areas where underwater pictures can be taken. Suspended matter, on the other hand, is highly variable both for different locations and at the same location with varying season and weather. It is the quantity of suspended organisms and particles that finally determine whether or not satisfactory pictures can be taken at a particular place or time.
OPTICS OF UNDERWATER PHOTOGRAPHY
In undersea photography it is general practice to use ordinary cine lenses computed for use in air — protected by a plane window. This introduces a water-air boundary which affects the focus and corrections of the lens. Objects under water appear nearer and larger both to the eye and to a camera. We have computed the effect upon focus and it turns out that the ratio of the air focus to that under water is equal to the index of refraction of air with respect to water. The