Camera and scene requirements
1. License plate must be readable and well-lit.
2. License plate dimensions must be at least:
● 150 pix for rectangular plates and 100 pix for two-row plates (for Kazakhstan, Armenia, Uzbekistan and Serbia).
● 130 px for rectangular plates and 70 pix for two-row plates (for all other supported countries).
NOTE: You should always set for rectangular plates.
3. Allowed tilt 5 degrees (clock and counterclockwise).
4. Vertical angle should not exceed 30 degrees.
5. Horizontal angle should not exceed 30 degrees.
Recommendations on mounting and adjusting.
1. If you want to recognize two or more lanes it is generally recommended to mount a camera on a crossbar.
2. We assume that you have IRLed if you want to recognize LP at nighttime.
3. Shutter speed must be big enough to cut the light from the car's headlights at night (usually it's about 1/1000).
But bear in mind, that too big of a shutter may obscure the edges of the lines (especially shadows).
But bear in mind, that too big of a shutter may obscure the edges of the lines (especially shadows).
4. Depth of focus is a very important parameter. If you are using a camera with a CSmount lens, use a fixed lens.
Fixed lenses are better for LP recognition due to greater depth of focus.
Fixed lenses are better for LP recognition due to greater depth of focus.
A megapixel lens is strongly recommended usually, they have M or MP marking.
5. When you'll be choosing the place of mounting, remember about sunrises and sunsets.
Direct sunlight beams can distort a picture. If the cars facing a direct sunlight use a lens with auto iris mode.
6. If you are mounting a camera on a roadside pole check how the pole reacts to heavy cars or a convoy of cars.
Some poles have tangible tremors. It will make LP recognition almost impossible.
7. If you tuned the camera perfect for the daylight wait for the night, and see what happens then (and vice versa).
8. If you don't know, how many pixels are in the LP take a fullframe screenshot and use a graphic editor (like photoshop).
Almost all of them have some kind of "ruler" tool.
Almost all of them have some kind of "ruler" tool.
9 It is generally advised to turn down WDR and BLC.
In most cases, they will make the picture more pretty, but at the cost of smudging small details (like an edges of letters in LP).
In most cases, they will make the picture more pretty, but at the cost of smudging small details (like an edges of letters in LP).
The same case goes with Digital Noise Reduction (it is recommended to have it low, at 1020).
10 On certain rare conditions there may be cases of false detections recognizing of fences, ads and other image parts that are structurally or semantically looks like a license plate.
To minimize this:
a. Adjust the roi accordingly. It may be a good idea to make it smaller, or change it’s shape, omitting the parts, which potentially may be false detected.
b. Adjust the min and max lp settings according to upper instructions do not leave a default 130300.
c. There may be cases, when the best performance will occur by changing angle of lens or moving the camera. In some cases, shooting a front lp is better.
11 To effectively capture the vehicle camera should be set so as to provide the minimum depthoffield (DOF).
Depthoffield (or length of the zone of sharpness) is the amount of distance between the nearest and farthest objects that appear in acceptably sharp focus in a video.
Depthoffield (or length of the zone of sharpness) is the amount of distance between the nearest and farthest objects that appear in acceptably sharp focus in a video.
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