DVC DigitEyes Series, Technical Manual, Page: 28 / 66

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5.6.6 Automatic Gain Control (AGC):
If this option is installed, the analog video output signal level is maintained at a preset (80 IRE)
level even if the ambient scene illumination varies. This is achieved by a feedback loop which
senses the average video output level and electronically controls the gain of the video
processing circuit to maintain the preset level of output video. The range of operation of the AGC
function is determined by the range of control of the video processing circuit and is
approximately 26 dB. It has a linear response.
5.6.6.1 AGC and Auto-Iris:
The range of automatic response of the camera to changes in ambient light can be extended
with the use of the Auto-Iris option. If this option is installed, it works in tandem with the AGC
function. As the scene illumination is decreased, the Auto-Iris lens "opens" wider until it reaches
it's maximum - after that, any decrease in scene illumination results in an increase of AGC gain.
5.6.6.2 AGC and Noise:
The increase of AGC gain increases the noise that is present on the video signal; the signal-to-
noise ratio of the analog video signal is considerably degraded in low-light, high gain situations.
However, some applications benefit greatly from the AGC and Auto-Iris functions. Since DVC
cameras have much higher signal-to-noise ratios than average analog video cameras, they
produce much less noise (even in low-light, high gain situations) than most competing products.
5.6.6.3 Automatic OR Manual Gain:
"Automatic" controls, such as AGC and Auto-Iris, are usually not suitable in applications where
absolute measurements are being made. If gain control is desired in such applications, the
manual OR computer controlled external gain control options are usually preferred.