Working with AGC and Open Shutter Settings

The SpeedDome Ultra VII Day/Night 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 situations. 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 3–5illustrates a Shutter Limit of 1/4.

Figure 3–5: Graphical view of Shutter Limit settings

Red Light

Red Light

Red Light

Green Light

250

250

 

180

msec

msec

 

msec

Configuring Camera Features

3–7