Poor IR contrast in new Tennessee license plates

wtimothyholman

wtimothyholman

IPCT+ Member
Nov 25, 2016
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I've noticed an issue with nighttime capture of new 2022 Tennessee license plates. The white lettering on a blue background washes out almost completely in IR light, making the plates barely readable.

Has anyone encountered similar issues with other plates? I'm wondering if additional IR illumination (beyond what the camera provides) might help.

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Those darn Moon Shine runners! Road grime/salt spray does that to some of my night images in Minnesota.
 
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wtimothyholman said:
I've noticed an issue with nighttime capture of new 2022 Tennessee license plates. The white lettering on a blue background washes out almost completely in IR light, making the plates barely readable.

Has anyone encountered similar issues with other plates? I'm wondering if additional IR illumination (beyond what the camera provides) might help.

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I started noticing the new plates and was wondering how well they would work with a LPR camera. Maybe they didn't mix enough reflective particles in the paint for the white letters? I think I get new plates this month.
 
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I don't think Dahua cameras "see" 740nm as well as they "see" 850nm. I could be wrong about that though.
 
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looney2ns said:
I would think more IR light in the 850nm range would still help.
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No, brightness is not the issue. It's lack of contrast. Below are a couple of the new plates, daytime and nighttime, from the same camera. At 850nm, the blue background and the white lettering have nearly the same reflectivity. You can see the plate just fine, but it's a white rectangle, with the characters unreadable by the LPR software 98% of the time.

I've talked to some people and I think I know what's going on. I was told that the new TN plates are specified for reflectivity at 740nm, which is the IR standard used in high-end LPR cameras for many years. The problem is that the pigments chosen for the new plates were not also tested at 850nm.

Supposedly the 740nm standard has been in place for years. The difference is that previous plates were also reflective at 850nm, but not by design, only serendipity. Unfortunately that's no longer true.

Any LPR camera that relies on 850nm IR illumination will be blind at night to a lot of TN and MS plates before the year is out. I've been told that Flock Safety is among those who are working to fix this issue with their own products. I suspect they'll be retrofitting a lot of cameras in the next few months.

And of course this also knocks out those of us who are using Dahua -Z12E varifocal cameras for DIY LPR. So I need to do some tests and see if 740nm illuminators will solve the problem.
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Hmm. I've been told that a local PD using Rekor cameras is having no problems, and Rekor operates at 850nm IR. If that turns out to be true, I'll try @looney2ns suggestion and experiment with a much brighter 850nm illuminator. I'm about 60 feet away from my roadway, so that might make a difference.
 
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I wonder if going into white balance and going to manual and adjusting the blue and red would reverse that night image and make the letters pop. Maybe try blue at 100?

No idea if that would work with IR or not, but worth a try since the camera will let you change it.
 
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wittaj said:
I wonder if going into white balance and going to manual and adjusting the blue and red would reverse that night image and make the letters pop. Maybe try blue at 100?

No idea if that would work with IR or not, but worth a try since the camera will let you change it.
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Agreed, I don't see how that would make a difference in B&W, but it costs nothing to try. I'll also try adjusting the contrast settings.
 
wittaj said:
Try swinging it both ways - maybe 100 and zero.

My state is the next to start getting new plates that I am afraid will have the same issues.
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More states are transitioning to printed plates as opposed to stamped plates. I suspect you may be right. I was told that the new Mississippi plates are doing the same thing.

I showed my images to an officer I know who tests new cameras for their LPR system. He's now gotten some PDs in surrounding cities involved in this issue, making tests on their own LPR cameras. They are very motivated to figure out exactly what's going on. Nobody wants their system to go "blind" at night.
 
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Seems like a pretty big blunder on some of these states to not think about this.

So many are going colorful with lots of designs that are dark with dark numbers printed. Every police dept should be lobbying their state to go with light plate with dark lettering and stamped if possible.
 
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it's the prisoners in the stamping room at the Prison....LOL...they FUBARRed the IR.....its a conspiracy. they're getting extra cigarettes in thier care packages now from El Chapo Guzman.
 
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I am surprised Tennessee didn't go with some rainbow colored musical note in the plate back ground. I wish the people who come up with ideas for Nashville and the state would break free from the music theme for once. Tennessee offers so much more than music. When I first moved here back in 1990, I had pictured in my mind Nashville as a bunch of Honkey Tonks with horse hitching posts outside. Well, I got one of the two images correct, anyways.
 
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