ALPR Camera Guidelines

Mar 27, 2023

Getting an optimal setup for performing ALPR can be a challenging task, the below information should serve to help answer some questions and provide guidance on how to get the best possible accuracy performance for any ALPR deployment.

Camera Positioning

Angle of Camera to plate should be less than 60 degrees
The best case scenario is a front-on view of the plate
Ideal License Plate size in frame is 75 ppf

ppf means pixels per foot density, which can be calculated by taking the Horizontal Pixels divided by Field of View width.

When positioning a Camera for ALPR purposes - the angle and distance relative to the scanned plates, as well as the lighting conditions are the primary factors to be considered. The optimal position for the camera would result in the plates being at a straight-on viewing angle level with the camera’s lens.

The lighting of the scene should also be considered in order to avoid excessive glare on the License Plates, as well as avoiding extremely low light scenarios unless IR sensors are being utilized.

Camera Specs & Settings

IR & RGB Supported
- For night time scanning, IR images are recommended
Minimum 2MP image resolution
Maximum of 160fps
FOV should be configured to achieve 75 ppf for License Plates
30fps with 1/100 Shutter speed is a good starting point

fps and shutter speed must be configured in regards to the speed at which plates will be moving in frame relative to the camera

When configuring your Camera for ALPR purposes - the resolution, FPS, and shutter speed should be the primary factors considered. For high speed movement a high shutter speed is important to reduce motion blur - in addition fps should be no lower than 10 in order to not miss fast moving vehicles.

The ALPR camera should ideally be a minimum of 2MP (1920x1080p) resolution. The camera FOV should be configured in order to achieve a minimum of 50 ppf for the license plates with an ideal number of 75 ppf or higher.