Poor IR contrast in new Tennessee license plates
- Thread starter wtimothyholman
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The problem is that the 740nm security illuminator currently on order is just as unknown a quantity as the 730nm grow bulbs that I bought. This equipment is being ordered from some unknown Chinese manufacturer, with performance and quality control being an absolute crapshoot. Is the 5241 really insensitive to 730nm infrared, or was the spectral output power of the bulbs the actual issue? All I can do is try some low-cost devices to experiment with, and hope for the best.
biggen
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It is odd that your illuminator worked on the PTZ camera though. That, to me anyway, suggests that the illuminator was working at the proper wavelength. Probably have to get @EMPIRETECANDY involved and see if he could get some emails going with Dahua on why it didn’t work on the 5231.
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It worked, but how well? The grow lamp has a significant visible red component, and that may be what the PTZ camera was picking up. The externally illuminated image still wasn't as bright as from the built-in 850nm IR diodes of the PTZ camera. If the overall sensitivity of the -Z12 is less than that of the PTZ, that might account for the results.
There are entirely too many unknowns. Lacking the equipment to do any optical measurements, and lacking any data about the no-name illumination sources, I'm stuck with trial-and-error experimentation. But what I do believe is this - there is no physical reason why a camera sensor that responds both to 850nm IR and visible light should not also respond to the 730nm to 750nm IR range. All the data I've seen on CMOS sensors shows that sensitivity is essentially monotonic between 600nm and 850nm.
If I have to, I'll spring for a Axton 730nm illuminator for my testing, which at least will be a piece of equipment that I can depend upon. But I'd dearly love to see a data sheet for the Dahua HFW5231E-Z12 or HFW5241E-Z12 showing optical sensitivity versus wavelength.
In the video he states this has been going on since 2007. He also states they ship the 730nm to Texas. I am using two 5241 z12's and have no issues with all of the different Texas plates that come thought. New ones, old ones, vanity plated, all are read just fine at night. No problem with contrast between the different backgrounds and the numerals.
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Texas uses plates that have black lettering on a white background. Tennessee did the same until this year. For whatever reason, the 3M manufacturing process provides sufficient contrast with the black letters. So this problem actually started years ago, but it didn't become obvious until now.
tigerwillow1
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I found out last night that new Oregon plates are also on this list. Here's a shot of a new flat plate with white letters on blue background going by my LPR camera. The older raised-letter plates are perfectly legible in the same situation.
DLONG2
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Where do you see an Axton 730nm illuminator? I see the 850s and 940s on their website.
Update: I like this zoom illuminator, as my plates are 200 feet away, and the IR has to cross a neighbor's front yard. This model can zoom to 20 degree x 10 degree: Zoom 15Z, Flexible Range IR Illuminator, Flexible Range Security Sys. IR ...
Update: I like this zoom illuminator, as my plates are 200 feet away, and the IR has to cross a neighbor's front yard. This model can zoom to 20 degree x 10 degree: Zoom 15Z, Flexible Range IR Illuminator, Flexible Range Security Sys. IR ...
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It's a special order for 730 nm IR diodes. You have to contact them directly.
DLONG2
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I currently have a 940 illuminator supplementing the camera's IR, which I like for it being invisible, but if the plates all change to where 730 is required then I'll go that route in spite of any distracting orange glow, darn it! ;-)
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It looks like more of 3M's "printed plate" technology. It's a great way for states to increase revenue with dozens of specialty plates. For law enforcement, it's a disaster.
My advice is to send some night images of these new plates to someone in a law enforcement agency that uses LPR cameras. That's what I did. Contact a reporter at a local news station, and also point them to the news stories about Tennessee's plates. I'd bet a week's salary that the LEOs in Oregon are aware of this problem, but no one wants to speak up and get his head chopped off. As a private citizen you may be able to raise awareness of this situation.
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There's a possibility that the 3M plates might actually provide good contrast at 940nm IR, despite being reflective at 850nm. But even if it works, the camera sensors won't be nearly as sensitive at that wavelength.
sebastiantombs
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Being a skeptical cynic and part time conspiracy theorist I have to wonder if this isn't the end goal, making LPR by the "normal citizen" more difficult or impossible? LEO will adopt to whatever it takes, they're funded by the "normal citizen". Then again there's the defund/weaken the police movement going on, too. Just letting what passes for my mind wander a little.
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"Never attribute to malice that which can be adequately explained by incompetence."
The states see 3M's process as a means of increasing revenue and reducing costs. If Oregon is like Tennessee, I'll bet it never even occurred to anyone to test the new plates with 850nm cameras, or with any LPR cameras at all.
We are all immersed in camera technology, and know all about it. But consider that inexpensive 850nm LPR camera technology is quite new. Flock Safety and Rekor didn't even exist until 2017. The rapid growth of (relatively) cheap LPR cameras in municipal deployment has happened so fast that most government officials have no clue they exist.
I am as cynical and conspiracy theorist as much as the next guy LOL, and I would like to think this is simply them not recognizing the unintended consequences of the plate change, but in talking to my higher ranking police buddies, they say it is intentional.
My one buddy was the FOP head for awhile and he said they would lobby to the state about these designs before a single plate was produced and said it would make their job more difficult and they were turned away. These lib democrats don't want the police to be able to have LPR in their cars scanning every plate that goes by and pulling over people with outstanding warrants and offenses. That is why we are seeing two-plate states go to just rear plate. The dems say it is cost savings, yet states that went from two plates to one actually had their yearly registration fee go up... The libs don't like front plates as it makes it easier for the police cruisers equipped with LPR to pull people over based on plates, and the lack of a square plate on the front makes it harder to use laser speed guns.
I am sure the states with toll roads that are automated with LPR and sends a bill to the vehicle owner will start to lose out on significant revenue.
My one buddy was the FOP head for awhile and he said they would lobby to the state about these designs before a single plate was produced and said it would make their job more difficult and they were turned away. These lib democrats don't want the police to be able to have LPR in their cars scanning every plate that goes by and pulling over people with outstanding warrants and offenses. That is why we are seeing two-plate states go to just rear plate. The dems say it is cost savings, yet states that went from two plates to one actually had their yearly registration fee go up... The libs don't like front plates as it makes it easier for the police cruisers equipped with LPR to pull people over based on plates, and the lack of a square plate on the front makes it harder to use laser speed guns.
I am sure the states with toll roads that are automated with LPR and sends a bill to the vehicle owner will start to lose out on significant revenue.
sebastiantombs
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I understand the drive to "rob Peter to pay Paul" that's built into every politician and hence every governmental entity, but I still wonder if there isn't some other motivation as well. These people aren't stupid and know thy can make tons of money off of automated traffic cams like stop light cameras and speed trap cameras. Then there's the toll roads that use LPR and make a ton of revenue that way, both for that special managing entity and the government coffers in general. It all combines to make me wonder, no proff I can cite, but the seed is there without a doubt to me.
Flintstone61
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Does the Illinois Tollway have camera's looking at fore and aft plates? They always seem to get me even If I go tight on a Semi...
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Tennessee is about as red a state as you could ever visit, with a supermajority of Republicans in the state legislature and government. I don't think that reasoning would apply here.
My own contacts in law enforcement told me they were rebuffed in their attempts to describe the problem, but not because of philosophical objections to LPR. It was good-old-fashioned "I'm covering my ass" and "We didn't make a mistake, so shut up and go away". Going up the chain of command got them nowhere.
It is probably occurring to companies like Flock Safety that they made a strategic error in assuming that 850nm IR technology would always work for LPR. We may even start seeing 730nm or 740nm IR as an option for some Dahua and Hikvision cameras if this trend continues.