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Problems of Controlling Correct Photographic Reproduction
By DR. H. MEYER, A. S. C.
PART III
The consistency of the negative developer is checked and kept constant by gamma control, and in Hollywood laboratories this gamma value has been generally set at approximately .68 plus/minus .05.
"Time and Temperature" versus "Test System"
The two developing systems referred to in the above are based on two different principles for controlling photographic reproduction of visual contrast as far as the negative processing is concerned.
In the "test system," negative tests exposed by the cameraman at the start of every scene which entails a changed lighting condition, are developed at an average standard time, and from a visual examination of each test the developing time which will render the best possible contrast and density in the corresponding actual negative scene is determined. This method, therefore, undertakes to keep negative contrast in each scene constant by varying the developing time and the developing gamma correspondingly.
In the "time and temperature system," the principal developing factors, time and temperature, and the developing gamma are kept constant. In this case it is entirely the cameraman's responsibility to control proper reproduction of contrast and brightness level by his lighting technic.
Theoretically, it should stand without argument that the "test system" be given unanimous preference in view of the additional help it offers to correct mistakes made by the cameraman in calculating exposure and lighting effects, which were, no doubt, made possible by the absence of proper methods or instruments for determining all existing relations between visual contrast and negative characteristics.
The decision in favor or against either of the two systems, however, is influenced by many practical factors, the discussion of which is not within the scope of this article.
Negative Types
While all laboratories, regardless of the developing system adopted, are accustomed to relying upon negative solution control with a fixed gamma value which is a characteristic, of course, of the film type used in connection with these control tests, it is frequently noticed that this procedure tends to form a habit which may unjustly become a reason for condemning film types differing in gamma from that of the film used for these control tests. This is particularly true of laboratories employing the "time and temperature system" when a difference in gamma is noticed while testing a new product against the controltest fiim type, it seems to upset the principle of consistency of developing time or speed so essential for this system of development. It has recently been prov
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