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.
hypersensitizing by mercury vapor has practically no influence upon the gradient as far as the useful part of the curve is concerned.
The increase in gamma of wet-hypersensitized panchromatic emulsions is largely due to the fact that bathing methods increase the sensitivity of panchromatic emulsions in the yellowish green and red-sensitive portions of the spectrum much more than they do in the blue. The original ratio of sensitivity, for instance, the blue-yellow or blue-red ratio, becomes changed, which means that the filter-factors of the wet-hypersensitized emulsions are different from those of the original emulsion. In this respect the dry-hypersensitized film behaves in a different manner. The mercury does not change the original sensitivity ratio in different wavelength regions; it appears that the increase of sensitivity is proportional throughout the portions of the spectrum to which the emulsion was originally sensitive. This method of dry-hypersensitizing apparently does not change the filter-factors of the original emulsion.
Film and plate emulsions from various manufacturers have been treated with mercury vapor, and no fundamental differences in behavior could be found. There is also no significant difference between the effect of mercury vapor upon ammonia and upon non-ammonia types of emulsions. It has been mentioned already that the action of mercury vapor is rather slow. At normal room temperatures, unwrapped films must be exposed to the vapors for at least twenty-four to thirty hours before the maximum increase of speed is attained. Longer treatment with mercury vapor does not increase the sensitivity to an appreciable extent, but the fog gradually increases. It would, of course, not always be practicable to treat unwrapped and unrolled films for thirty hours in an atmosphere containing mercury vapor. However, it has been found that it is not at all necessary to unwind and unwrap the films completely. The penetration of the mercury vapor into spooled and tightly rolled material is surprisingly uniform and efficient, making the whole process much more practicable and convenient. It is, for instance, sufficient to leave a 1 000-ft. roll of motion picture negative film in the original can, and put a few drops of mercury wrapped in porous paper inside the empty space of the film core. The film can must be closed and sealed with tape, and should stand for approximately six to eight days. During this period an increase in speed extending very uniformly throughout the entire I 000-ft. roll can be noticed. The same effect can, of course, be attained with regular rollfilm spools or with spools for the Leica and Contax cameras. In the latter case it is not necessary to open the original cartridge; it is sufficient to put the whole cartridge into a small container containing mercury.
Stability of Dry-Hypersensitizing
The hypersensitizing effected with mercury vapor is not permanent. The speed gradually recedes over a period of about four weeks; after which a more or less stable condition is reached when the sensitivity of the material is somewhat below that of the emulsion before the treatment. However, during the
Page Fi ve