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92 Transactions of S.M.P.E., July 1927
cost or a matter of increasing the size of the negative image and making the prints by projection. There is a good deal to say about making prints in an optical printer as against printing by contact. The camera being built for this purpose is called the "Magnigraph," and I think there is a great deal to be said on this point.
New Hyper-sensitizing Process. — G. Seeber announces that a Japanese investigator has discovered a gas that can be used for this process, especially for cine film. It has been found that several gases act energetically on silver bromide, a few of them in a very short time, while others act so strongly that an accurate dose can not be administered. As is well known in the majority of cameras the length of film actually free from the magazines is comparatively short, but this is sufficient for the gas to get in its work. The great advantages of this method are first, that it is a dry method; the film is hyper-sensitized only just before exposure and there is no after fogging, as the film immediately leaves the gas zone. For commercial work it is suggested that a vent pipe may be fitted to the camera to allow excess gas to escape. Increased gas pressure as well as increased temperature gives greater sensitivity. It has not yet been determined how the gas acts, but provisionally it is assumed to be by catalysis. It is also said that a mixture of gases can be used as a color filter and that a color-sensitiveness is attained, such as has not yet been dreamed of. The gas may be dissolved in a liquid, as acetylene is in acetone, and a small bottle of 50 ccs. capacity, will suffice to sensitize 1200 meters of normal film. Such a small container may be placed inside the camera, or in the tripod head. It has also been suggested that the legs of metal tripods might be filled with the dissolved gas. "The cameraman of the future will be in the position at any time not only to instantly increase at will the sensitiveness of the film, but also by simultaneous use of the gas to make it color-sensitive. This special possibility will work out in the most favorable way in taking films in natural colors." (Phot. Ind. 1927, 25, 329).