Poor IR contrast in new Tennessee license plates
- Thread starter wtimothyholman
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- Nov 25, 2016
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This is NOT with the 730nm light source. I'm still waiting for that to be delivered, but first I wanted to be certain that I could image plates at 850nm.
- Nov 25, 2016
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It's being shipped from China. Arrival is estimated to be Mar. 10. Hopefully it will be early.
Smilingreen
Known around here
You were onto something. Local MSM finally runs the story.
www.newschannel5.com
Tennessee's new plates aren't readable by license plate readers at night
License plate readers are coming to Davidson County for a test run very soon, but NewsChannel 5 has learned the state’s new plates may be an issue.
www.newschannel5.com
- Nov 25, 2016
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My 730nm IR bulbs arrived today. They look good - sturdy and nicely constructed. I tested both of them in a standard light fixture, and used an indoor Amcrest PTZ camera in IR mode to see how bright they were.
The result so far? They definitely appear very bright in IR mode, easily illuminating the entire room. It looks as if my choice of a 30 degree lens angle was a good one, and the camera sensor had no problem at all with 730nm illumination.
To the human eye, they are a deep red, but not distractingly bright. No doubt people will wonder about those two red lights on the corners of my front porch at night, but they shouldn't be a distraction to drivers. I'll do some installation and testing this weekend once the rainstorms move out of the area.
The result so far? They definitely appear very bright in IR mode, easily illuminating the entire room. It looks as if my choice of a 30 degree lens angle was a good one, and the camera sensor had no problem at all with 730nm illumination.
To the human eye, they are a deep red, but not distractingly bright. No doubt people will wonder about those two red lights on the corners of my front porch at night, but they shouldn't be a distraction to drivers. I'll do some installation and testing this weekend once the rainstorms move out of the area.
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Awesome! Can't wait to see the outside videos!
Do they cast a red glow?
Do they cast a red glow?
- Nov 25, 2016
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Yes, but they're not that bright to the human eye. They're not exactly covert, but most people will probably walk right past them and never give them a second thought. Plenty of people have all kinds of external LED illumination for their homes, so this will probably be dismissed as more of the same.
If it works I will just say I was lazy and didn't take the Christmas color light out 
- Nov 25, 2016
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Or maybe people will think I'm trying to illuminate my front yard without ruining anyone's night vision.If it works I will just say I was lazy and didn't take the Christmas color light out
I hope it works because this would be an economical solution compared to some of those high priced illuminators.
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These bulbs come in a range of power levels, from 7 W to 36 W, but with the same form factor. I went with the 7 W version based on the power levels of professional illuminators. The heat sinks are overkill, but that is not a bad thing when it comes to operational lifetime.
If it works, I am so going for the 36W lol. More is better right LOL.
- Nov 25, 2016
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That may be too much of a good thing. I suspect I'll have to dial back the settings of my LPR cameras significantly compared to the built-in LEDs. We shall see.
I hope you are right! My concern is how far out their reach is.
Hopefully you have an overview cam you can slow the shutter down and take a video showing us the reach of these LEDs
Hopefully you have an overview cam you can slow the shutter down and take a video showing us the reach of these LEDs
- Nov 25, 2016
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I've done some preliminary tests, and so far things are not looking good with the 730nm IR LED bulbs.
Despite being bright enough for me to easily aim by watching the red glow of the bulbs from reflective surfaces across the street, they weren't bright enough to illuminate a license plate from 65 feet away with standard LPR settings on my Dahua IPC-HFW5231E-Z12 camera. I turned off the IR LEDs in the camera, and relied solely on the 730nm bulb for my tests.
As a sanity check, I pointed the 730nm bulb at my parked car about 30 feet away, which is normally being recorded by my Dahua SD49225T-HN PTZ camera. The brightness of the image was significantly reduced with the 730nm bulb illuminating the scene versus the internal LEDs of the camera.
At this point I'm a bit puzzled. The power output of the 730nm bulb should be comparable or greater than the power output of the 850nm LEDs in the cameras, and if anything the sensors should be more sensitive to the shorter wavelength IR. Yet overall performance is much worse.
There are higher power bulbs available, but I'm reluctant to try one. At 7 W, the bulbs are very noticeable from the street. Stepping up the power might result in the bulbs distracting passing drivers, which I do not want to happen.
Despite being bright enough for me to easily aim by watching the red glow of the bulbs from reflective surfaces across the street, they weren't bright enough to illuminate a license plate from 65 feet away with standard LPR settings on my Dahua IPC-HFW5231E-Z12 camera. I turned off the IR LEDs in the camera, and relied solely on the 730nm bulb for my tests.
As a sanity check, I pointed the 730nm bulb at my parked car about 30 feet away, which is normally being recorded by my Dahua SD49225T-HN PTZ camera. The brightness of the image was significantly reduced with the 730nm bulb illuminating the scene versus the internal LEDs of the camera.
At this point I'm a bit puzzled. The power output of the 730nm bulb should be comparable or greater than the power output of the 850nm LEDs in the cameras, and if anything the sensors should be more sensitive to the shorter wavelength IR. Yet overall performance is much worse.
There are higher power bulbs available, but I'm reluctant to try one. At 7 W, the bulbs are very noticeable from the street. Stepping up the power might result in the bulbs distracting passing drivers, which I do not want to happen.
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Bummer. I was afraid of that.
I just don't think that bulb is designed for the distance. When you looked at it on the camera, did it seem like a wide dispersion or was it more narrow?
I have been looking for a bulb like that where they would list the effective range but that doesn't seem like people are using it for that.
I just don't think that bulb is designed for the distance. When you looked at it on the camera, did it seem like a wide dispersion or was it more narrow?
I have been looking for a bulb like that where they would list the effective range but that doesn't seem like people are using it for that.
- Nov 25, 2016
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I purchased a bulb with a lens angle of 30 degrees, based on calculations and diagrams I'd seen for professional illuminators. The beam was narrow enough that I could point it at a road sign and see the reddish reflection. I wanted a broad enough beam to cover the width of the roadway at 60 to 70 feet distance, and in that respect it seemed a reasonable match. The beam required some aiming, but it wasn't so narrow as to make the aiming process extremely sensitive.
But clearly the 730nm portion of the spectrum didn't have the range I'd hoped for. Since this bulb is intended for indoor plant cultivation, it may be that I'm missing something fundamental in my assumptions. But ... if I can see the reddish visible portion of the spectrum's Gaussian distribution being reflected off a sign from 70 feet away, why can't my camera pick up the 730nm portion reflected from a license plate at the same distance? It's puzzling.
I'm guessing the same way that a piddly led flashlight can reflect off a sign that far away but clearly isn't providing enough light to be effective at that distance.
I guess we need to investigate the IR on cameras because from the street the red glow of a bullet looks the same as that of a turret,but the bullet range is further. Is it strictly a wattage thing or is there something we are missing that is flawing the 730nm option.
Probably wouldn't make a difference, but what about b/w with I think it is called the electrical option (I think it is electrical and ICF or something like that as two options) and see if that picks it up?
Or if you can see the red reflection, what about adjusting the red on the color balance?
Just brainstorming ideas to try to make it work.
I guess we need to investigate the IR on cameras because from the street the red glow of a bullet looks the same as that of a turret,but the bullet range is further. Is it strictly a wattage thing or is there something we are missing that is flawing the 730nm option.
Probably wouldn't make a difference, but what about b/w with I think it is called the electrical option (I think it is electrical and ICF or something like that as two options) and see if that picks it up?
Or if you can see the red reflection, what about adjusting the red on the color balance?
Just brainstorming ideas to try to make it work.