Working With Agc And Open Shutter Settings - American Dynamics SpeedDome Ultra VII Operator's Manual

Working with AGC and Open Shutter Settings

The SpeedDome Ultra VII dome provides settings for compensating for low-light scenes in
color: Automatic Gain Control and Open Shutter. Automatic Gain Control (AGC) amplifies
the video signal in scenes with minimal light. Many low-light scenes result in picture noise.
As gain is increased, the picture noise is also amplified.
When AGC is enabled, the camera automatically adjusts the gain setting value. When AGC is
disabled, no gain is applied to the video signal. This may make the video appear darker on the
monitor.
The gain setting for the camera differs from the maximum gain (Max Gain) setting available
on the Camera Functions menu. The Max Gain setting is an upper limit for how much gain
can be increased when AGC is enabled. The trade-off between picture level (brightness) and
noise may be adjusted by setting the Max Gain value. Lower values for Max Gain setting
may result in a darker picture with less noise. Higher values for Max Gain setting may result
in a brighter picture with more noise.
In addition to the AGC settings, you may also adjust the Open Shutter settings to improve
dome performance in low light conditions. For more information, continue with
Understanding How Advanced Shutter Settings Improve Low-Light Performance.
Understanding How Advanced Shutter Settings Improve Low-Light Performance
The camera dome supports the ability to view color images from extremely low-light
situations. This feature is called Open Shutter and is only in effect during low-light situations
where an image would not be obtainable otherwise. It does not affect the camera performance
in normal or bright light situations.
When the Open Shutter is enabled and the scene illumination is too low to obtain a clear
image at the normal video rate, the camera collects luminance information from multiple
fields. As it does so, the current video information is retransmitted until new information is
available from the camera. Under these conditions, moving objects will appear blurred, and
still images may appear blurred, choppy, and with more static than video obtained under
normal lighting conditions.
The Shutter Limit value sets the video update time in fractions of a second. Depending on the
lighting conditions, the video information may be updated more frequently, but no slower
than the limit set.
Figure 3-1 illustrates a Shutter Limit of 1/4.
Figure 3-1: Graphical view of Shutter Limit settings
Red Light
Configuring Camera Features
Red Light
250
msec
Red Light
250
msec
Green Light
180
msec
3-5