LESSON 3
reproduction. The highest gamma obtainable in any particular emulsions is
called "gamma infinity". It depends on the emulsion and, to a lesser
degree, on the composition of the developer used. Typical gamma infinity
values for some different types of emulsion, when processed in the
developers normally used for them, are as follows:
(1) High speed portrait film 1.2
(2) High speed press film 1.7
(3) Commercial film 2.0
(4) Process film 3.0
b. Timetemperature charts. Recall that one of the primary factors
governing the density of an image is the temperature of the developer. The
higher the temperature, the greater the activity of the solution, therefore,
shorter developing times are needed. As the temperature drops, the
developing time must be increased. Since gamma must also be considered,
typical time temperature charts include a gamma value which varies according
to development time and temperature. Designation of this value allows you
to control development in order to produce a desired gamma. By consulting a
timegammatemperature chart, which is published by the manufacturer of the
film, you can determine the proper developing time under varying conditions.
A typical chart of this type is shown in Figure 31.
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