One of the biggest challenges with setting up a reliable LPR /ANPR camera system is getting the night time license plate capture dialed in just right. Watch this night-time video demo to see the testing that we recently performed with our new Viewtron IP based LPR system. You can also watch this video of the day time LPR testing that we made did last week.
Night-time video surveillance is more challenging than day time to begin with. License plate recognition (LPR) and automatic number plate recognition (ANPR) is extremely particular because of lighting conditions, vehicle headlight / tail lights, the vehicle’s motion, and the reflective material that plates are made of.
Here are some installation tips based on our recent testing and 14 years of experience in supplying security systems.
Here are some things that need to be considered when planning an automatic license plate capture system.
1) Use a Genuine LPR Camera. If you want reliable license plate capture, you must specifically use an LPR camera. LPR cameras are designed to capture plates by using specialized hardware and software. If you are not using an LPR camera, DO NOT expect to get good results.
It does not matter if the camera is ultra high resolution. Resolution is not the main factor. Also, please note that some cameras support LPR (license plate recognition), but not ANPR (automatic number plate recognition). The Viewtron LPR camera that was used to make the above video supports both.
2) Low Angle of View. The angle of view matters a lot when it comes to LPR camera installation. Notice in the below picture how low we mounted our LPR camera. The less of angle to the license plate capture zone (both vertical and horizontal), the better the success rate for license plate detection and number recognition. You do not want more than a 15 degree angle in either direction. THIS IS EXTREMELY IMPORTANT!
The more level and a tightly focused on the plate area, the better.
3) Pair ANPR Cameras with Overview Cameras. LPR / ANPR cameras are designed specifically to capture vehicle number plates and they need to be tightly focused on the plate detection zone. I good rule of thumb is that LPR cameras should be focused on a single lane of vehicle traffic. For this reason, they should always be paired with at least one overview camera to provide surveillance coverage of the surrounding area / record an overview of vehicles.
This is what it looks like at night when the LPR-IP7 records license plates. This is the view on the NVR. You can see that it does a great job of license plate reading / character recognition and logging the plate information to a database, but the plate is all you see.
This is why we always pair LPR camera with at least one over view camera. Here is the 4 channel view on the Viewtron NVR so you can see the view with the two overview cameras.
4) Night Settings. Most commercial grade LPR cameras have the ability to have settings for day time and night time surveillance. We ran multiple tests and ended up using the following settings night time on our LPR-IP7 camera.
Here are some notes based on what we learned.
- Brightness: It can be kept around value 25 in day mode, and in night mode it’s suggested to be lower value to see the license plate clearly.
- Max. Shutter speed: 1/500~1/1000; if the vehicle speed is lower than 40KM/H, it can be extended appropriately, but no more than 1/100;
- Min. Shutter speed: 1/10,000; Exposure mode: Auto Gain Mode: Auto Gain limit: recommended not to exceed value 20
- It Is also recommended to switch between day mode and night mode by schedule; On the night mode schedule make sure you force the camera into B/W with IRs on. And switch two sets of parameters through schedule.
Typical Day Settings： Brightness=25; Shutter Max=1/500; Shutter Min=1/100000; Gain=10
Typical Night Settings： Brightness=5; Shutter Max=1/500; Shutter Min=1/100000; Gain=10
5) License Plate Detection Settings. LPR and ANPR are also functions of the recorder being used. This is the Viewtron IP camera NVR that we use with our LPR systems.
The Viewtron NVR has a configuration section specifically for license plate detection and recognition.
For the best results, the license plate detection zone should be as small as possible. Do not select the entire screen. Select only the area where plates pass through and specify accurate plate sizes.
The best way to do this is to park a vehicle in the detection zone and choose a minimum and maximum plate size that is slightly smaller and slightly larger than the plate you use for setup. On the Viewtron NVR, you can check the display range checkbox to see a visual as you adjust this setting.
Complete ANPR / LPR Systems
CCTV Camera Pros supplies this pre-configured LPR / ANPR camera system that includes the LPR camera, overview camera, and NVR used in the above video. This system is designed to monitor a single lane of traffic. By the way, the overview cameras are AI security cameras with built-in vehicle and human object detection.
We can add additional LPR cameras and over view cameras to this system if you have additional areas where you need video surveillance. For example, a home owners association typically wants to monitor both incoming and outgoing traffic.
This system costs much less than comparable license plate capture systems and it performs better in our testing. The LPR and ANPR software that is built into Viewtron NVRs make is an outstanding value. Many other security manufacturers charge an additional license fee for these functions.
Please let me know if you have any questions about this article or need help designing a security camera system. You can email me here.