to the overall system.
FIGURE 1-1.
Theoretical system transfer characteristics
2.
To help clarify contrast and the transfer characteristics, the
following examples are given to illustrate the use of gamma other than 1.
a. If an unattended monitor camera were placed outdoors where it was
subjected to sun reflection and required to monitor the passage of dark and
light objects, the contrast range would be far greater than the camera or
system could faithfully reproduce. A large amount of picture detail would
be lost in the white or black end of the reproduced gray scale.
b. By using a system gamma of less than 1, the wide range of input
luminance could be effectively compressed into a narrower range of output
luminance, which could be handled by the reproducing kinescope, and the
picture detail and relative luminance in the original scene would be
faithfully reproduced.
3.
Refer to curve b of figure 1-1.
This represents the transfer
characteristic for a theoretical system with a gamma of 0.5.
For such a
system, a change of input luminance of 100-1 produces only a 10-1 change in
output luminance, which is ideal for the lighting conditions described.
a. On the other hand, where it is necessary to transmit information
from a photographic plate or x-ray negative having a narrow contrast range,
a system having a gamma greater than 1 would be more useful.
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