License plate readers have become a fact of life for law enforcement. Cities around the country are adding them to their arsenal of law enforcement equipment to crack down on traffic violations and other crimes.
They are becoming popular because a license plate camera can operate autonomously without taking the time of an officer. This saves money and frees up police for more important tasks like investigations, responding to emergencies and responding to felony crime reports.
License Plate Recognition Types
Right now there are two types of license plate readers on the market to satisfy differing requirements. In one case you may only want to be able to make out a license plate number on the video from the camera and in the other case, you want the license plate recognition system to automatically record the license plate numbers along with the picture of the car.
License Plate Readers
Although it’s natural to feel that the higher the resolution of a camera the better. It may be counterintuitive but, this may not always be the case. Particularly in low-light situations, higher resolution cameras take longer to resolve an image and may take in too much information in relation to the license plate itself to give a clear image. In other words, the higher resolution may give a better overall picture at the expense of the license plate itself. A 1 MP camera may be all you need to get the job done.
A big problem with some cameras is their wide angle field of view. They can read a plate, but not if it’s further away than about 15 feet because the angle is too wide. Get a camera or lens with a narrower field of view around 10 feet or less at more than 25 feet.
To achieve up to 40-50 feet performance make sure you get a high-quality variable focus lens in the 25-40 mm.
License Plate Capture
Some buyers need to be able to capture the license plate number to a database for further analysis. As good as license plate readers are they don’t give you the ability to do anything with the license plate number right from the record. The number is still only readable not ready for passing on to a database or search algorithm.
FPS rate and camera resolution required depends to a large degree on the application. If you are capturing from city streets where the cars are traveling at less than 50 mph, 4 frames per second and VGA resolution is good enough. Higher speeds may require faster fame rates.
Software is also a very important aspect of the equation. This article does not touch on software.
For more information on both hardware and software and some real-world testing please see the great article license plate recognition – milestone lpr, ipconfigure, openalpr by networkcameracritic.
For more information on how to set up an Auto LPR system, please read another great article Setting up an automatic license plate recognition system by Doug Wyllie.
In any case, make sure you purchase a license plate recognition (LPR) camera designed specifically for the task. Heather Klotz-Young in her article 5 Ways to Measure up LPR & Non-LPR Cameras points out the 5 critical differences between LPR and non-LPR cameras.
- Level of performance – LPR cameras still hold the edge over non-LPR cameras in performance
- Lighting – LPR cameras are better designed for varying lighting conditions than non-LPR cameras
- Shutter speed – While slower shutter speeds of some non-LPR cameras may suffice for slow-moving vehicles on side streets, LPR cameras will be able to handle most any vehicle speed on city streets or highways
- Field of view – Non-LPR cameras traditionally have a wider field of view than LPR cameras which usually focus on just the license plate. Of course, the most important consideration of license plate recognition is the readability and usability of the license plate number so whatever uses you might think you have for the wider field of view, don’t let it detract from your main focus.
- Cost – Budgets are tight and the lower cost of non-LPR cameras is enticing. Test the cameras and make sure they do what you need them to committing to the lower-priced cameras.
Take a look at our picks and see if one is the perfect camera system for you!
License Plate Readers
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Thanks for reading! We sincerely hope this article has given you valuable information that will help you choose the best license plate readers for your organization!