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.
The increase of speed attainable with this ireJ-hypersensitizing method, as it might be called, amounts to 100 per cent, more or less, depending upon the type of emulsion used. Emulsions that have been made in the presence of ammonia usually show less increase of speed.
To make the special treatment practicable, for instance, with panchromatic cine negative film, great care had to be observed in manipulating the wet films, and redrying the emulsion carefully was particularly important to the quality of the results. In addition, hypersensitized films always have certain disadvantages, especially with regard to their keeping qualities, which will be discussed later.
With the introduction of the supersensitive types of negative film, interest in these inconvenient, cumbersome, and expensive methods of hypersensitization declined considerably.
Yet, even with the availability of the supersensitive types of panchromatic materials there still exists, and probably always will, a demand for higher sensitivity, if possible without increasing the graininess.
General
Upon investigating the effect of mercury vapor upon photographic emulsions, it was found that the sensitivity of nearly all types of negative emulsions can be considerably increased when dry films or plates are exposed to the action of mercury vapor.
In our original experiments, photographic emulsions upon films and plates were exposed to the action of mercury vapor by placing them into a lighttight container, the bottom of which was covered with a thin layer of metallic mercury. In the container, films and plates were treated for approximately thirty hours, after which the emulsions showed an increase in sensitivity of about 75 to 150 per cent, depending upon the type of emulsion and upon the mercury vapor concentration within the container.
In Fig. I the difference of sensitivity between the untreated material and the material hypersensitized by mercury can be seen, and in this particular case is about 75 per cent. It is interesting to note that the characteristic curve of the mercury-hypersensitized emulsion runs almost parallel to the curve of the untreated material. This fact is pertinent because wet-hypersensitized materials usually show a distinctly steeper gradient than the untreated materials, as will be seen in Fig. 2.
In Fig 2 the characteristic curve of the untreated material, A, is plotted together with the curve of the same emulsion treated with mercury vapor, B. The third curve, C, is for the same emulsion again, but hypersensitized by one of the wet-hypersensitizing methods. In this case a small amount of ammonia in distilled water was used as the hypersensitizing solution. In Fig. 2 the wethypersensitized emulsion shows a somewhat steeper gradient than either the type emulsion or the emulsion dry-hypersensitized by mercury vapor. This increase of gamma is characteristic of wet-hypersensitizing methods, while the
Page Three