This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
A shutter operated by air pressure, a bulb and tube being used for the purpose of operating it. Pressure on the bulb drives the air through the tube, forcing a small piston rod to release or operate the shutter.
An instantaneous or time shutter made of a strip of opaque cloth in which is an aperture that permits of the lens being uncovered and again covered, thus permitting of the exposure being made. One form of this shutter which is placed close to the sensitive plate is termed a focal-plane shutter; another form, working on the same principle, can be placed either in front of or behind the lens.
A very efficient type of shutter, working between-the-lens cells, giving practically accurate speeds up to 1-150 of a second. Manufactured by Goerz.
A very efficient type of shutter, working between-the-lens cells, giving practically accurate speeds up to 1-150 of a second. Manufactured by Bausch & Lomb Optical Company.
(See Back Swing.)
A silhouette portrait is a profile view of the face, the whole image being black and contrasting against a white background. There are various ways of producing silhouette portraits. The easiest one, perhaps, is to place the sitter near a brightly illuminated translucent screen (securing a profile view). The plate should be slightly under-exposed. When the negative is developed the head will be represented by clear glass, while the background will contain a dense deposit of silver. A print from such a negative will give a silhouette portrait.
Silk, satin and other fabrics may be printed upon with very effective results. The silk best suited for the purpose is that known as Chinese silk. Before sensitizing any fabric it should be first washed in warm water containing a good lather of soap, then rinsed in hot water, and gradually cooled down until the final washing water is quite cold. The cloth is sensitized in identically the same manner as paper, full instructions for which is given in the text.
A metal of a white lusterless color. Soluble in nitric and in hot concentrated sulphuric acids; insoluble in hydrochloric and in cold diluted sulphuric acid. Used principally in photography in the manufacture of silver nitrate, which latter is used in sensitive emulsions.
AgBr. Bromide of Silver. Yellowish powder. Soluble in concentrated ammonia; in solution of potassium cyanide and potassium bromide; also in solution of sodium hyposulphite. Insoluble in water, alcohol and ether. Its uses in the various sensitive emulsions, both for plates and papers, are very important. Bromide of silver is sensitive to light, although no visible change takes place when so exposed for a short period of time. The change which has taken place may be tested by adding to a solution of the salt any alkaline developing agent which will immediately turn the solution black.