Poor IR contrast in new Tennessee license plates

biggen

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Ahh. I'm still waiting for a TN plate at night. So far all I have is one guy driving during the daytime only I'm afraid. Or, maybe he has driven by at night and I can't read it. I really wish I could buy a TN plate. I looked on eBay but only old plates are for sale there. Nothing new yet.

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Ahh. I'm still waiting for a TN plate at night. So far all I have is one guy driving during the daytime only I'm afraid. Or, maybe I can't read it at night...

View attachment 125039
Your best chance of catching a Tennessee plate will be early in the evening, while there is still some ambient light but your camera is in B/W mode. Search for B* as a wildcard.
 

Flintstone61

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Mn plates are now flat printed plates as well. Have been for quite a few years. But I'm catching those and Wisconny. Wisconsin Has some tattered ass plates. I don't think they can put down their beer long enough to figure out how to make a plan like Minn. Every X number of Years in Mn they issue you new plates when you renew your stickers.
 
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@wtimothyholman the issue you find is correct, i checked with dahua engineer for this external IR.
This lens is limited by the infrared confocal problem. The transmittance of the lens itself at night is as follows, and the transmittance below 800nm will be poor.

View attachment 125090
@EMPIRETECANDY, this is one time I wish I had been wrong. So there is no hope of using the 5231 camera with a 740nm infrared source.

Do you know if the newer 5241 camera has the same limitation? Will any Dahua camera with an adjustable focus have this limitation?
 

EMPIRETECANDY

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@EMPIRETECANDY, this is one time I wish I had been wrong. So there is no hope of using the 5231 camera with a 740nm infrared source.

Do you know if the newer 5241 camera has the same limitation? Will any Dahua camera with an adjustable focus have this limitation?
Yes, same on 5241 too. That may need a special project to do this change, not sure if need any hardware change. I will make some checking.
 

wittaj

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Here is something interesting LOL. I will post it in another thread as well, but certainly speaks to what you are seeing.

So I was watching my cameras live and tweaking between color and B/W and other tweaks I am always doing and notice this non-descript plain white truck go by so I got suspicious:

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So I pull up a color camera to see what is going on and this is the truck:

1650592199688.png

That is unbelievable and exactly what your plates are doing. Now that you know it is a Kroger truck, you can kinda see it in the B/W photo, but wow!

Now imagine if this were someone that had damage done to say a parked car hit by this vehicle and all they had were B/W cameras going, nobody would suspect this truck!
 

kferrero

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Here is something interesting LOL. I will post it in another thread as well, but certainly speaks to what you are seeing.

So I was watching my cameras live and tweaking between color and B/W and other tweaks I am always doing and notice this non-descript plain white truck go by so I got suspicious:

View attachment 125886

So I pull up a color camera to see what is going on and this is the truck:

View attachment 125887

That is unbelievable and exactly what your plates are doing. Now that you know it is a Kroger truck, you can kinda see it in the B/W photo, but wow!

Now imagine if this were someone that had damage done to say a parked car hit by this vehicle and all they had were B/W cameras going, nobody would suspect this truck!
That is certainly wonky behavior, in B/W mode the camera is concluding the box and cab are the same shade of color. From the B/W shot you'd think this truck was all white when it very clearly is not. This definitely offers some insight into whats happening with the TN plates, the camera thinks the whole plate is white in B/W mode. I'm curious if theres anything in software that can fix this or if its a hardware problem.
 
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That is certainly wonky behavior, in B/W mode the camera is concluding the box and cab are the same shade of color. From the B/W shot you'd think this truck was all white when it very clearly is not. This definitely offers some insight into whats happening with the TN plates, the camera thinks the whole plate is white in B/W mode. I'm curious if theres anything in software that can fix this or if its a hardware problem.
It's very much a hardware problem, but it can only be solved if you illuminate the truck at a different infrared frequency than 850nm, and if your camera is sensitive to that new IR frequency. If two colors reflect equally well at 850nm wavelength IR light, then they will appear to be the same shade of gray (or white) to the camera sensor.

There is no fixing this with software; Rekor and Flock Safety have tried, with very little success. If there is little or no contrast between the foreground and background colors under 850nm IR light, there's nothing for the optical character recognition software to work with.
 

samplenhold

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If there is little or no contrast between the foreground and background colors under 850nm IR light, there's nothing for the optical character recognition software to work with.
This right here.

Not a software issue. Not a hardware issue. There is nothing wrong with the software or the hardware. They are performing as intended.

The problem is that at 850nm, those colors have very little contrast.

That is certainly wonky behavior, in B/W mode the camera is concluding the box and cab are the same shade of color.
That is not true. There is no 'color determination' by the camera. The cam does not sit there and look at the scene and determine that two colors are the same and then displays it in black and white as the same shade of grey. The sensor is picking up reflected IR light and is sensitive to the wavelength around the 850nm band. Every optic system, whether it be biologic or electronic, perceives an image in specific electromagnetic bands. Your eyes can't see cellphone signals, but they are there. Just like your eyes can't see IR at 850nm.

EM Specrum.JPG
 

kferrero

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This right here.

Not a software issue. Not a hardware issue. There is nothing wrong with the software or the hardware. They are performing as intended.

The problem is that at 850nm, those colors have very little contrast.


That is not true. There is no 'color determination' by the camera. The cam does not sit there and look at the scene and determine that two colors are the same and then displays it in black and white as the same shade of grey. The sensor is picking up reflected IR light and is sensitive to the wavelength around the 850nm band. Every optic system, whether it be biologic or electronic, perceives an image in specific electromagnetic bands. Your eyes can't see cellphone signals, but they are there. Just like your eyes can't see IR at 850nm.

View attachment 127662
Good points and yes I agree, I live in TN, I still have one of the old style plates but I'd love to get an illuminator at 750nm to test the theory out. Anyone know where you can buy an IR illuminator with 750nm LEDs?
 
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Good points and yes I agree, I live in TN, I still have one of the old style plates but I'd love to get an illuminator at 750nm to test the theory out. Anyone know where you can buy an IR illuminator with 750nm LEDs?
Read the rest of this thread. I've already gone down this path. You can buy 730nm or 740nm illuminators, but the Dahua camera models that most of us use for LPR are insensitive to those IR wavelengths, as confirmed by @EMPIRETECANDY. They are optimized for 850nm IR, and are essentially "blind" below 800 nm.

So basically there isn't much to be done, beyond hoping either the state releases new plates, or some camera manufacturer offers a suitable LPR camera that works at shorter IR wavelengths.
 

kferrero

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Read the rest of this thread. I've already gone down this path. You can buy 730nm or 740nm illuminators, but the Dahua camera models that most of us use for LPR are insensitive to those IR wavelengths, as confirmed by @EMPIRETECANDY. They are optimized for 850nm IR, and are essentially "blind" below 800 nm.

So basically there isn't much to be done, beyond hoping either the state releases new plates, or some camera manufacturer offers a suitable LPR camera that works at shorter IR wavelengths.
Fair enough, I've read the State's response and unsurprisingly they refuse to admit there's an issue and are not going to spend any more money on redesign, even though they also admit they did zero LPR testing. Outside of heavy pressure from law enforcement, I think waiting for a newer camera is the only option at this point, sucks.
 
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Fair enough, I've read the State's response and unsurprisingly they refuse to admit there's an issue and are not going to spend any more money on redesign, even though they also admit they did zero LPR testing. Outside of heavy pressure from law enforcement, I think waiting for a newer camera is the only option at this point, sucks.
Unfortunately, this entire mess was a combination of bad decisions and bad politics. The Dept. of Revenue screwed up because it never occurred to them to test the plates. Once the nighttime visibility issue was revealed, Flock Safety screwed up by claiming they could fix the problem in software, because they have thousands of their cameras deployed in TN and they didn't want their customers to lose faith in the product.

But once Flock said, "We'll fix it!", that gave the Dept. of Revenue the excuse they needed to do nothing. And now Flock has a whole lot of cameras that are slowly going "blind" at night as the new plates are deployed. There's nothing they can do short of total replacement of every deployed camera in the U.S.

The older vendors with more expensive custom cameras (e.g. SkyCop) do have 740nm cameras, so as far as they are concerned this is a great situation for them. Either you buy their cameras, or you won't have a functional LPR system. But companies like Flock Safety, Rekor, and every other vendor with 850nm cameras are now between a rock and a hard place.
 

Maxdog

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Hi - I'm interested in building a DIY LPR system and I live in TN. Has anyone found a LPR camera in the price range of the Dahua that utilizes 730 IR illumination?
 
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Hi - I'm interested in building a DIY LPR system and I live in TN. Has anyone found a LPR camera in the price range of the Dahua that utilizes 730 IR illumination?
I have not. I've spoken to a police officer, and according to him the situation is only getting worse as more of the new plates are issued. Both Rekor and Flock Safety have been tweaking their LPR software to improve IR readability, but there's only so much that can be done when the contrast between the letters and background is so poor.

What I can recommend is this: even if your LPR software can't read the plates at night, at least the human eye can generally figure what the plate says if you examine several frames. What I've resorted to doing is using SecuritySpy to provide a timestamp of whenever a car passes by my house at night. I also record continuously from my LPR camera feeds. If something suspicious happens and my LPR camera doesn't read the plate, I can search through my recordings using the timestamps from the vehicles going by, and read the plate manually.

So I'm stuck with an LPR system that reads almost everything during the day, and almost nothing at night. The glass is definitely only half full.
 

Maxdog

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Thank you wtimothyholman for your reply and all of the great info on this topic. I'll keep digging to see if I can find an affordable camera that will work in the 730 nm wavelength, and I'll post the info if I find anything.
 
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