Low Cost License Plate Capture ShootoutBy Derek Ward, Published May 21, 2014, 12:00am EDT (Research)
License plate capture (LPC) is very popular as shown by our License Plate Capture Shootout 2014's high member interest.
One challenge is that purpose built LPC cameras can get quite expensive, even an inexpensive one, like the Geovision MP LPC we tested, runs ~$1,000.
We decided to test 4 low cost integrated IR IP cameras, all $200 or less, including Dahua, Hikvision and Q-See models, to see if they could deliver effective license plate capture.
We tested at slow speed (~5mph) and higher speed (~30mph), day and night, like so:
And we created image comparisons for each of the 10 runs (including various shutter speeds), that look like so:
For background on fundamental issues in capturing license plates, see:
Here are our key findings from this test:
- Using default settings, all cameras were able to capture plates at slow (~5 MPH) and fast (~30 MPH) speeds during the day.
- No cameras were able to capture plates using default settings at either speed at night.
- Given the poor illumination patterns of these lower cost integrated IR cameras, overexposure of the highly reflective plate was a problem, requiring faster shutters speeds for reliable capture, substantially darkening the overall scene.
- Since the vast majority of low cost integrated IR cameras use fixed lenses, properly selecting one to match the mounting location, lane width, etc., may be problematic, reducing performance.
- Among the low cost cameras tested, the Hikvision DS-2CD2032-I bullet performed best at both slow and fast speeds due to a more even illumination pattern, capturing plates at shutter speeds as low as 1/750s. Other cameras required 1/1000s and up for reliable capture.
- The Q-See QCN7001B performed worst in our tests due to a very bright IR hotspot causing overexposure of plates, requiring 1/2,000s shutter speed for reliable capture at ~5 MPH, and failing to capture plates at ~30 MPH even at 1/10,000s shutter.
Comparative camera pricing is as follows:
- Avigilon 2.0W-H3-BO1-IR: ~$650 USD estimated street price
- Dahua IPC-HFW3200SN: ~$200 online
- Hikvision DS-2CD2032-I: ~$170 online
- Hikvsion DS-2CD2232-I5: ~$200 online
- Q-See QCN7001B: ~$150 online
For low speed license plate capture, these low cost integrated IR cameras may work, with substantially faster shutter speeds than default. Given their low price, installing two cameras (using one for capture and one for scene overview using default settings) is possible for less than the cost of one dedicated specialized license plate capture camera (~$850 and up).
For faster speed license plate capture, 30 MPH and up, they may work, but IR pattern and range will likely be bigger issues than at slower speeds. Performance should be verified in the field before relying on them for capture.
IR Illumination Patterns
One of the key differentiators for low cost IR cameras and their ability to successfully capture a license plate is their IR illumination patterns. Cameras with hotspots in the middle of the FOV and uneven IR patterns require faster shutter speeds to compensate for a heavily illuminated image.
For example, below is a comparison image of the Hikvision DS-2CD2232-I5 and the Hikvision DS-2CD2032-I. Compared to the 2232 from our 2013 Hikvision IP Camera Test, it's hot in the middle but not nearly as hot, and less noisy.
Slow Speed Comparisons (<10 MPH)
We then tested the cameras performance at slow speeds, ~5-10 MPH in a commercial parking lot. Cameras were set to capture two lanes, or a ~22' HFOV.
Below is the Daytime FOV with the license plate captures of each camera at default settings with a 1/30 sec shutter speed. As seen in our street daytime testing, all cameras are able to capture the plate of the test car.
We tested in this same FOV at night, as well:
1/30 Shutter Speed
Similar to our street scene, cameras are unable to capture a license plate of a moving car even at ~5 MPH with a 1/30 second shutter speed, due to motion blur and overexposure of IR illumination on the plate.
1/500 Shutter Speed
At 1/500 second shutter speed, we get a clear image of the license plate with the Hikvision DS-2CD2032-I in this scene. All others are able to only partially grab plate characters or are washed out due to ir illumination.
1/1,000 Shutter Speed
With 1/1,000 shutter speeds, both Avigilon and Dahua can capture the plate, similar to our street testing.
1/2,000 Shutter Speed
At 1/2,000 shutter speeds, the Q-See and Hikvision DS-2CD2232-I5 are able to get a clear view of the plate when the test car is traveling ~5 MPH in our parking lot location.
High Speed Performance
We first tested daytime performance, with our test vehicle travelling about 30 MPH. The 5 cameras were left at default settings, with a 1/30 sec shutter speed. All cameras were able to successfully capture the car with minimal motion blur as well as grab a clear image of the license plate.
At night, the lux levels remained at ~15 lux due to an overhead streetlight directly above the cameras. Below is the general FOV used for testing. All cameras were left at default settings, with adjustments being made exclusively to shutter speeds.
1/30 Shutter Speed
Starting at the defaults from the daytime testing, we can clearly see that no camera out of the 5 we used for testing was able to get a clear ID off the license plate.
1/250 Shutter Speed
Speeding up the shutter to 1/250 seconds, the license plate becomes less washed out and blurry. Still, no camera is able to capture a clear license plate.
1/500 Shutter Speed
At a 1/500 second shutter speed, the Avigilon and Hikvision 2032-I are able to produce a partially legible plate, while the Dahua, Hikvision 2232-I5 and Q-See are still significantly blurry and washed out.
1/750 Shutter Speed (Hikvision cameras only).
While testing for the next fastest shutter speed, it was noted that both Hikvision cameras had 1/750 shutter speeds, which was a speed no other camera tested had available. At this speed, the Hikvision DS-2CD2032-I captured a plate clearly, while the 2232-I5 could not.
1/1000 Shutter Speed
At 1/1,000 seconds shutter speeds, the Avigilon is able to get a clear read of the plate in this scene, and the Dahua 3200S captures a blurry plate, with some characters legible.
1/2000 Shutter Speed
Shutter speeds 1/2,000, the Dahua and Hikvision 2232-I5 get clear reads of the license plate. However, the Q-See does not come close to capturing a plate.
Q-See Fails to Capture
At shutter speeds of 1/4,000 and 1/10,000 per second, the Q-See QCN7001B is incapable of capturing a license plate of a ~30 MPH moving car at night.
The following are examples of nighttime plate capture with all cameras at varying settings.
In this video, we have compiled all of the successful passes of each camera in the parking lot scene. Note that the vehicle is traveling ~5 MPH in a ~1 lux scene.
In this example, we have footage of each camera that was able to capture the license plate at their optimal shutter speeds for this test. Cameras are shown in alphabetical order.
In this second clip, we have compiled each pass with the Q-See 7001B at every progressive shutter speed. Users will notice that the Q-See was unable to capture a license plate at any shutter speed.
Cameras were tested using default settings at 30 FPS, unless otherwise noted. All cameras started at 1/30s shutter speed, which was sped where necessary. Cameras were tested one at a time so IR illumination interference was not an issue, with the vehicle moving past at the specified speed multiple times to check capture.
Cameras were integrated to Exacqvision version 220.127.116.11050 without issue. The following firmware versions were used:
- Avigilon 2.0W-H3-BO1-IR: 18.104.22.168
- Dahua IPC-HFW3200SN: 2.420.0000.0.R, build : 2014-04-14
- Hikvision DS-2CD2032-I: V5.1.2 build 140116
- Hikvsion DS-2CD2232-I5: V5.1.2 build 140116
- Q-See QCN7001B: 2.100.QS00.9.R, build : 2012-12-07
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