Capturing license plates is a common desire for both residential and business owners.
Capturing plates is the most difficult task security cameras perform. The challenges are considerable. The target is usually moving, the camera must be at the right angle to the movement of the vehicle, the horizontal field of view of the camera must be adjusted so the camera has enough resolution at the target location to capture the plate. The camera must compensate for the glare of the headlights or tail lights and the reflective nature of the plates. Getting all these variables to line up for reliable plate capture can be challenging.
The first step is to follow the camera location rules for plate capture. If the camera is not located to view at the correct angle and height, there is little chance of capturing every plate that passes by. The following camera locations and target field of view must be followed.
There are two distances that matter when locating the camera.
A) The distance from the camera to the target location of the plate. Max 120 Feet
B) The horizontal viewing distance at the location of the plate. Max 15-20 Feet
Both distances can be accommodated by using a camera with an adjustable zoom lens. The zoom lens allows you to adjust the camera's field of view so you have a horizontal view distance of no greater than 20 feet at the target location.
The best location for plate capture is a natural bottleneck that funnels the traffic into a narrow entry such as a drive entrance. This helps because the natural traffic flow requires each vehicle to line up with the camera's target location as they enter and exit.
The most common mistake consumers make is trying to use a camera for general surveillance and capture plates. This causes the consumer to select a horizontal viewing distance which much wider than is required, usually 40-60 feet at the target location. Plain and simple it will not work, even with 4K cameras. To capture license plates you must dedicate one camera to the job following our Pros Golden Rules - One camera, one job and keep the horizontal viewing distance under 20 feet.
Using 4K Surveillance Cameras to Capture Plates
Many of our customers use our general surveillance cameras to capture plates. While the resolution and lens zoom capability of these cameras allow you to meet the distance requirements we discussed above, they lack the specialized AI and image adjustments that LPR cameras offer. Below is a sample video showing plate capture using our Pro240MZ general surveillance camera and other 4K cameras. While the performance is excellent compared to other cameras on the market, they still do not perform as well or offer the features of a true LPR camera.
Why you should use a LPR camera for license plate capture?
LPR cameras are equipped with enhanced features. They offer glair reduction filters, 60 frames per second recording, and AI software for target identification.
Glair & Reflection Reduction
The biggest challenge to capturing plates at night or in low light is the glair created by the vehicle's headlights and tail lights. In addition, the camera must be able to compensate for the light-reflective nature of the plates. LPR cameras have advanced image filters that allow you to adjust the performance of the camera in all lighting conditions.
Moving Vehicles & Frame Rates
LPR cameras are equipped with a video chip that can capture 60 frames per second of video. Regular surveillance cameras offer a maximum of 30 frames per second which is considered "real-time". If a vehicle is moving it is best practice to record as many frames per second as you can. The faster the vehicle, the more frames you want. Because LPR cameras double the frame rates they capture clearer images when the vehicle is in motion. This feature coupled with an adjustable shutter speed allows the camera to be adjusted to its environment.
AI & Target Identification
LPR cameras are equipped with advanced AI capabilities. The camera can identify a moving vehicle, locate its license plate, capture an image of the vehicle and a zoomed image of the plate, all while automatically adjusting to changing light conditions.
The camera communicates with the video recorder via a network cable, usually Cat6 cable which connects the camera to the recorder or a common network with PoE.
Recording, Database & Management
The LPR video recorder receives the data and creates a searchable database of all plate captures. The system offers white and black list automation responses. If you have a database of plates that should enter a certain location the system will read the plate and compare it to the database. If a plate is not listed in the databases alerts can be automatically sent to responding parties.
The recorders searchable database allows a user to quickly search the data and locate all images of a specific plate or find all plates entering a specific location or time frame.
Installation & Setup
LPR systems are designed for the application. Each requires some setup to adjust the camera and recording to the environment and the customer's needs. Our LPR systems are preconfigured from the factory to make the setup process as fast and simple as possible. The customer needs only to install the equipment and then call our technical center for complete setup and adjustment support.