The Dictionary Of Photography

A True Historic Record Of The Art & Practice Of Photography 100 Years Ago.

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Vivisoope                                                                 Wastes
When the so-called Russian vignettes or images on a black ground are required, a very good method is to use a vignetter in front of the lens or between the lens and the plate. When used in front of the lens a card or metal plate with the particular shaped opening is supported in front of the lens, and gently moved backwards and forwards an inch or two during exposure, the distance in front of the lens being found by adjustment. When used in the camera the most convenient form is that of an American invention which is practically a large iris diaphragm placed about a third of the focus from the lens. Obviously cards or metal plates may be used in the same way.
Viviscope. See Zoetrope and Cinematograph.
Voice, Photographing the. Czermak, in 1862, photographed the vocal cords in action, and in 1878 Professor Blake, who worked in the laboratory of the Brown University (U.S.), obtained very minutely denned records of speech itself. A beam of sun-light was reflected from a small mirror, so suspended that every movement of a telephone disc would alter its angle. This beam was received on a sensitive plate moved by clockwork.
Vulcanite. Syn. with Ebonite (q.v.).
Washing Negatives and Prints. - Upon the perfection of the washing process practically depends the life of negatives and prints, as the presence of hyposulphite of soda, or silver, tends to fading of negatives and prints, and yellowness of the whites of the latter. There are numerous commercial washing tanks and troughs, which answer their purpose admirably. Running water is the most effective means for the elimination of the undesirable faults, but when the water supply is limited, the prints or nega-tives should be allowed to soak in water for ten minutes, and then the water changed ; and this operation repeated six times will usually be sufficient for negatives and prints. Messrs. Grundy & Haddon have proved that ten minutes' thorough wash-ing is quite sufficient to eliminate all the hyposulphites that can be eliminated, and it is a recognised fact that very prolonged soaking of prints in water is liable to initiate a decomposition of the organic matter of the films.
Wastes. See Residues.
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