In this example, the dome receives information about the color of the traffic light. While the light is red, the image is relatively static. With the shutter limit set to 1/4 second (250 milliseconds), updated red light information is transmitted at 1/4-second intervals. When the light changes from red to green, updated light color information becomes available. The dome must now transmit information about the green light. This update occurs as soon as the green light information is available. This may occur before the 1/4-second interval elapses. In this example, the light changed to green after

180-milliseconds. Thereafter the green light information is transmitted at 1/4-second intervals until new light color information becomes available.

If the light were to change from red to green halfway through the field integration interval (125 milliseconds), it may appear that both the red and green lights are on simultaneously. This situation is illustrated in Figure 3–6.

Figure 3–6: Mixed field integration

Red Light

Red Light

Red/Green Light

Green Light

250

125

 

125

msec

msec

 

msec

Adjusting the Shutter Limit sets the update time used to maintain the image quality. If you want to videotape an incident in low-light conditions, you may find that tape quality is not acceptable. To ensure that the videotape quality is acceptable for possible prosecution purposes, you may want to test the Shutter Limit settings under the expected lighting conditions.

The Relationship between IR Mode and AGC and Open Shutter Settings

The current IR Mode setting affects which AGC and Open Shutter settings are available. The following table lists which AGC/Shutter modes are available based upon the IR Mode setting:

 

IR Mode Setting

 

 

AGC Off

 

 

AGC On

 

 

Open Shutter

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Off

 

 

Yes

 

 

Yes

 

 

Yes

 

 

 

 

 

 

 

 

 

 

 

 

 

 

On

 

 

Yes

 

 

Yes

 

 

Yes

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Auto High

 

 

Yes

 

 

Yes

 

 

No

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Auto Mid

 

 

No

 

 

No

 

 

Yes

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Auto Low

 

 

No

 

 

No

 

 

Yes

 

 

 

 

 

 

 

 

 

 

 

 

In addition:

 

 

 

 

 

 

 

 

 

 

•When AGC Off is the current setting, the Max Gain and Limit fields are not displayed.

•When AGC On is the current setting, the Max Gain field is displayed and may be modified. The Limit field is not displayed.

•When Open Shutter is the current setting, both the Max Gain and Limit fields are displayed and may be modified.

3–8

SpeedDome Ultra VII Day/Night Operator's Manual