If the default exposure settings do not produce acceptable results, you can adjust the
iris, shutter time, and gain settings of the SharpV
ALPR camera to work best with your outdoor installation.
Before you begin
Ensure that the lighting conditions match what is expected during normal camera operation.
In a correctly-exposed license plate image, the
characters and the plate state are dark and well-defined, and the background is
white or very bright.
IMPORTANT:Modifying the exposure
settings can greatly impact ALPR performance. You must test the system after
modifying these settings.
In the ALPR image, it is normal that the surroundings
of the plate are under-exposed while the plate itself is correctly-exposed. Make
sure that the plate is correctly exposed and ignore the quality of the
surroundings.
The ranges for the Exposure time and
Gain settings must be large enough to allow good quality
images in all lighting conditions, but you should reduce the range as much as
possible. If the range is too large, it increases the risk of over-exposure or
under-exposure. It is normal that the SharpV
constantly varies the exposure of the ALPR camera in order to get a correct exposure
of a plate.
Modifying settings to improve read performance at night can have a negative impact on read performance during the day, and vice versa. Therefore, you must test the settings both at night and during the day (under sun illumination).
If the SharpV is expected to read both
embossed and flat license plates, perform the day instructions with the flat plate
and the night instructions with the embossed plate.
Procedure
Adjust the ALPR camera under sun illumination:
Place a stationary license plate as close to the
camera as possible while still being within range for the camera to capture plate
reads.
From the Configuration menu,
click Cameras > Exposure.
From the Select your camera menu,
select the ALPR camera.
The live feed from the ALPR camera is displayed. Do
not modify the focus. The license plate might appear out of focus, but you are
only adjusting the exposure in these steps.
From the Exposure drop-down list, select Range (outdoor).
Gain, Exposure time and Iris settings are displayed.
Set the Gain and Exposure time minimum and maximum levels to their minimum values.
Clear the Iris check box.
Move the Iris slider towards the right as much as possible without over-exposing image.
When you are satisfied with the appearance of the plate images in the video feed window, click Save.
The system displays the message Configuration saved successfully.
Adjust the ALPR camera at night:
Place a stationary license plate as far from the camera as possible while still being within range for the camera to capture plate reads.
From the Configuration menu, select Cameras > Exposure.
From the Select your camera drop-down list, select the ALPR camera.
The live feed from the ALPR camera is displayed. Do not modify the focus. The license plate might appear out of focus, but you are only adjusting the exposure in these steps.
From the Exposure drop-down list, select Range (outdoor).
Gain, Exposure time and Iris settings are displayed.
Increase the Exposure Time maximum as much as possible without getting an over-exposed image.
If the Exposure Time is set at the maximum value and the image is still dark, increase the Gain maximum until you are satisfied with the image.
When you are satisfied with the appearance of the plate images in the video feed window, click Save.
The system displays the message Configuration saved successfully.