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Nonsilver Photographic Processes
By THOMAS T. HILL
A number of nonsilver photographic, or light-sensitive systems such as those based on diazo dyes, have been used or proposed for specialized purposes. None of them, as yet, exhibits the sensitivity or the wide applicability of the silver process. This survey of the current status of these systems will discuss current limitations as well as possible future prospects with particular reference to the field of motion picture engineering.
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'EFINED BROADLY, photography is a very widespread field. It includes all those systems by which an image can be made more or less permanent, an image resulting from an exposure to some type of light. Occasionally we see mention of new systems of photography and though they are often very promising, we are still working with the silver system of photography. So, the question arises, "Why haven't some of these other possibilities come into use?"
This paper will review some of these other possibilities, their advantages and their disadvantages in comparison with our current silver system, and discuss what we are likely to hear from them in the near future.
First, however, we must note that, while we grumble about the shortcomings of the silver emulsions which we now use, the necessity of processing them in solutions and finally the necessity of using them properly, they are
Presented on April 24, 1952, at the Society's Convention at Chicago, 111., by Thomas T. Hill, The Edwal Laboratories, Inc., Ringwood, 111.
really very versatile and set a high mark of accomplishment against which to compare the new possibilities. Examples of the wide versatility of silversalt photography are easy to find, ranging from astronomical photography to photomicrography.
A discussion such as this one develops a new respect for the silver system, in that it is applicable to so many aspects of our work. On examination, we find that many of these newer light-sensitive systems are of narrow ranges of usefulness.
Photographic chemistry is but a branch of photochemistry, which studies all reactions caused by or accelerated by exposure to light. Among the many photochemical reactions are some which appear to be bases of new photographic systems, but which on further study are either so insensitive or have so limited an application that they are not really practical.
Among the possible light-sensitive systems of interest to us at present are the following (some of these, of course, are physical as well as chemical systems) :
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July 1952 Journal of the SMPTE Vol. 59