Reading License Plates at Night, Light Reflection / "overexposure". HID / Xenon, standard bulbs

niko

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#1
There will never be a fully perfect dash cam ( as with all technology ). People want always more and more and more. But from few dozens of dash cams I have tested ( half of them were so called premium class priced over 200usd ) - DOD LS300W video quality can be compared with high end models ( if not better in most cases ).

About cars numberplate readings ( reflection ) at night I want to start new tread, but I was not sure if it was discussed here yet or not ?
We can discuss this very important issue and each member can share his own experience / knowledge.

HID / XENONE Bulbs, NUMBERPLATE READINGS AT NIGHT:

At night, very important for numberplate reading will be two factors:

1. do you use standard bulbs or HID / Xenon. If standard bulbs, then numberplate readings are good from most angles. If HID / Xenon, then there will be a reflection from the front car numberplate till the moment when your lights will not shine exactly directly onto the front car numberplate.

2. If front car numberplate is on the white background ( like most European cars ), or on some other ( non-white ) background.

a) If white numberplate background, then it is very hard to read a number because direct HID / Xenon light will be bouncing back directly into your camera and overexposing whole car numberplate, so you will not be able to read numbers.

b) If non-white numberplate background, for example in UK cars have front numberplate background white, but rear numberplate background is yellow, so the reading of numberplate which are with yellow background is much better than if it would be white. The best cars numberplate to read / record if your car has HID / Xenon is for example Chinese cars where depending on province ( or some other factors ) they are using blue, green and black colour numberplate background. From those numberplate HID / Xenon light of your car bulbs is not reflecting that much ( not over-reflecting ), so reading is the best compare to EU car numberplate.

P.S. Using polarized filter on your dash cam at night can reduce front car numberplate reflection, so you can read it, but dramatically darkens everything what is around the car, it will be almost pitch-dark, in many cases you will not see even what car type / model it is, so polarized filters are no good to use for night driving.

This HID / Xenon reflection issue is common to all dash cameras no matter what price. It's just laws of combination: optics / cmos / cpu, which is hard to overcome within small price that today's dash cams cost. Only high-end professional movie cameras can sort out this issue, but they cost tens ( hundreds ? ) thousands of $.

Sorry for my english, but hope you know what I was trying to explain.

P.S. - thanks to DashCamMan to bounce my post into a new topic.
 

DashCamMan

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#2
Re: Reading License Plates at Night. HID / Xenon, standard b

This is an interesting thread since I think you captured most of the factors related to poor night performance. The other factor is ambient light. If you are driving down a city street with lots of street lights and store lights, that will help in seeing details. While dark country roads will perform worse.
 

jokiin

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#3
Re: Reading License Plates at Night. HID / Xenon, standard b

Just to add to this (it is a great subject by the way as people often judge performance on how well number plates can be read) having HID or Xenon lights is a benefit for just about everything 'other' than reading number plates, you're right that Chinese number plates are much easier to read, and very often what you see used in any example footage, in Australia if this was happening 20 years ago we'd have no trouble reading any plates, after that though the speed camera reared its ugly head and the government introduced reflective number plates, the sole purpose of these plates is to be able to be read at night with the equipment they use, a very high powered flash mounted off axis and cameras designed specifically for the purpose of catching the plate within a fixed field of view, would never make a great dash cam but it's great at raising revenue

I guess each country around the world has done the same, makes it a challenge to get a decent result with a set of headlights pointing directly at something with so much reflection, many street signs have the same reflective properties and can be read fine at night, viewed off axis though it is much easier, point your headlights directly at the sign and the same problem would exist

This is certainly a challenge from a manufacturing perspective, some customers expect great results under any lighting conditions or circumstance, I don't think that's entirely possible with current technology but things are always improving
 
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niko

niko

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#3
I put together short video clip of recent test-drive just showing how can Xenon / HID lights ( also works for standard bulbs as well ) affect video recording of license number plates. It's all depends on light angle bounces back from numberplate into the camera. I did few screenshots of front moving car and how difference in few seconds can change recording results depending on light angle reflecting from number plate.
Test was from Capacitor based G1W-C from Foxoffer.



Xenon HID (1).jpg

Xenon HID (2).jpg

Xenon HID (3).jpg

Xenon HID (4).jpg
 

CheckYourLights

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#3
I have HID fogs and headlights, but my windshield is tinted 30% charcoal Llumar ATR. Plates come out well. And only have a cheap DVR027
You happen to live in one of the very few states that allow the windscreen to be completely tinted. Most states at least to my knowlage only allow a tint strip to the AS-1 line
 

REyewitness

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#5
We have noticed this reflection from the plates also. Any idea if the light colour temp. Has any bearing on the ability to read a plate? I have 6000k and reflections are bad if you follow anywhere near 2 second follow rule. If plate is high up, like mini van or SUV then its no problem.
 
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niko

niko

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#6
We have noticed this reflection from the plates also. Any idea if the light colour temp. Has any bearing on the ability to read a plate? I have 6000k and reflections are bad if you follow anywhere near 2 second follow rule. If plate is high up, like mini van or SUV then its no problem.
I think its all about colour temperature. If you see my video very beginning, where I parked my car ( without my Xenon / HID ) lights on, only car-park lights, then you can read Toyota Avensis number plate, but as soon as I turn on the Xenond / HID lights, - then Toyota number-plate is going white, because too much light is reflecting back from number plate background. I guess with standard bulbs it would not be that dramatical, but I didnt had standard bulbs in any of my cars for over many years, always like to "pimp my ride" from very first day I buy car :)
 
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#8
Plate-reading isn't a big problem if you can capture the vehicle for more than a few seconds, since your HIDs will dip and there will be a frame (or several) legible. That's all it takes! Otherwise, you have the make/model, trim level, all these distinctly physical characteristics that will usually be sufficent for identification. Recently: our Honda Element had vestigial "spikes" on top from the Thule roof rack system. That's an identifier. My wife's Acura TL had several trunk badges indicating trim level (as well as a dealer badge I eventually got rid of). My old Nissan 370Z was sufficiently rare in these parts, plus visible were the orange seats (which made it more rare). And there are always front windshield stickers.

The point is, there are many markers and other things that serve to prevent cars from being totally anonymous without inclusion of the plate, although the plate # will assist the police in locating a hit-and-run driver. (And BTW these are exactly the sorts of things you'd want to remove or disguise if you were using your car for nefarious purposes. :)
 

CheckYourLights

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#9
The point is, there are many markers and other things that serve to prevent cars from being totally anonymous without inclusion of the plate, although the plate # will assist the police in locating a hit-and-run driver. (And BTW these are exactly the sorts of things you'd want to remove or disguise if you were using your car for nefarious purposes. :)
A few other members and I talked about this before and I am glad more people think this way. It must run in car enthusiast (with you driving a Fairlady Z before. Myself a Z/28).

Between driving what seems like one of the last few Z/28s that have not been totaled in my area and what I am sure will be the only one with a CB Radio in it even if i was ever looking to make a get away I couldn't stick out anymore if i wanted.

I am not a huge fan of the HID light craze going on. Mostly because people here use them incorrectly. They use the wrong color temperature so while they get what they think is the neat purple look they get less useable light and it is splattered everywhere because along with the wrong color temperature the don't use the correct housing.

I do see more and more new cars use the correct light set up Stock though and some people do set them up correctly in non stock applications so it is nice seeing some progress made and that there is some technology in the pipe line to address it in time.
 
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#10
I am not a huge fan of the HID light craze going on. Mostly because people here use them incorrectly. They use the wrong color temperature so while they get what they think is the neat purple look they get less useable light and it is splattered everywhere because along with the wrong color temperature the don't use the correct housing.
The 8000-degree Kelvin lights are a joke ... annoying, but you have the satisfaction of knowing the owner is probably replacing bulbs every 3rd trip he makes. The housing is a more serious problem; my neighbor who should know better (because he used to own a car shop) got the $150 Ebay Special, and so now when he drives down the street it's the same as high beams. He must wonder why he can't get any brighter than that, but the answer is because his lens housing doesn't have a top cutoff.

Anything over 5000-degree Kelvin, which is what a lot of OEM HIDs are, reduces your vision when you're driving in precipitation, because the blue light scatters back more from water droplets. Fogs should be at 2400-Kelvin or lower (yellow) to actually assist your vision.

I don't know how most [reflective license plates] are designed -- googling the 3 words leads you to a 3M marketing website but I didn't stay around long enough to understand the technology. I suspect (hope) that if you only have a single flared license plate image to try to identify a car, you might be able to photo-manipulate the image down to a readable one.
 

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#12
It is not legal in my state. But my vehicle is exempt because its considered an emergency vehicle.
Oh. I seen your post says you live in Florida I had just read online that it is legal in Florida and a relative that lives in West Palm Beach happened to mention it a few years ago bit I haven't had tinted windows in years. Looking again some sites say it's okay some say AS1 line only

When I was younger I did the 5 percent all the way around and had one those subwoofer boxes in the back of an F Body but I'm a little to old for the blacked out windows and window rattling stereo anymore.
 
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#13
Florida is front two windows are 28% give or take 5% for manufacturing difference. Windshield to the AS1 line. And rear windows is 15% give or take 5%.
The windshield strip can be as dark as you like.
 

GET

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I believe there is a solution for a problem. Technically it is possible to change camera settings depending on current conditions. Camera is able to detect night conditions or to change mode using some presets and local sun rise/set times. There is a linux library for that. Most popular cameras like BlackVue, FineVu, Panorama use Linux inside. Better picture analyzing is also possible. Dash camera's purpose is to make a record of some fact on the road. It should not make a nice movie for watching. Readable license plates are part of "proof-ability" of the record. So, dash cam algorithms should be changed. There are image algorithms for geting more details in light areas at the expense of details in dark areas. This is just a question of R&D expenses.
 

Sungmoon Jang

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#15
I believe there is a solution for a problem. Technically it is possible to change camera settings depending on current conditions. Camera is able to detect night conditions or to change mode using some presets and local sun rise/set times. There is a linux library for that. Most popular cameras like BlackVue, FineVu, Panorama use Linux inside. Better picture analyzing is also possible. Dash camera's purpose is to make a record of some fact on the road. It should not make a nice movie for watching. Readable license plates are part of "proof-ability" of the record. So, dash cam algorithms should be changed. There are image algorithms for geting more details in light areas at the expense of details in dark areas. This is just a question of R&D expenses.
Panorama is not linux solution.
Also my company is struggle to see the plate number in high reflection condition.
I dare to say, it is almost done.
The result can be shared within few days.
I also expect alot about this effect.
 

GET

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#16
The result can be shared within few days.
I also expect alot about this effect.
Good to know! Thank you!

And it is a bit sad that Panorama is not a Linux solution. I'd like to play more with it. Usually community helps much to make things better. But I like PowerUCC customer support and way it does things.

BTW, have you seen following comparision: http://auto-dvrs.ru/reviews/panorama-ii-vs-lukas-lk-7900-vs-finevu-cr-500hd/

It is in Russian, but I think you can evaluate videos and shots. There is a Panorama II, Lukas LK-7900 ACE and FineVu CR-500HD. That time Panorama showed good result, but it was worse of that 3 cameras especially in dark conditions. However, I bought this camera, because I believe PowerUCC may fix many things and they are willing to do it instead of companies like Blackvue.
 
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Panorama is not linux solution.
Also my company is struggle to see the plate number in high reflection condition.
I dare to say, it is almost done.
The result can be shared within few days.
I also expect alot about this effect.
That sounds interesting! Will this be a firmware upgrade available for current Panorama owners? Or will it only be part of a new model?
 

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#18
Just bouncing this old thread - I just wondered if the firmware @Sungmoon Jang refers to was ever released please?

Basically I do a lot of night driving and finding it a nightmare finding anything that can handle numberplate reading at night

Also if this is fixed in the Panorama does this mean the same workaround is in place in the jnew Panorama Z please?

What is the current recommendation for better dashcams that can handle HID headlights at night?

Thanks in advance :)
 

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#19
Just bouncing this old thread - I just wondered if the firmware @Sungmoon Jang refers to was ever released please?

Basically I do a lot of night driving and finding it a nightmare finding anything that can handle numberplate reading at night

Also if this is fixed in the Panorama does this mean the same workaround is in place in the jnew Panorama Z please?

What is the current recommendation for better dashcams that can handle HID headlights at night?

Thanks in advance :)
I also would to find a solution to this problem. Our plates are black letters on a white reflective background. Which are a nightmare to decipher in the dark.

It's interesting to know that Police forces have had Automatic Number Plate Reading systems for a few years in the UK. Does anyone know if they work at night?
 
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#20
Maybe a yellow filter might help without reducing light. I use a yellow pair of sunglasses when its raining and it drastically reduces glare. I also used to use these when riding in low light, dusk/dawn so I could see wet patches easier in very shady areas covered by trees.



A lot of ski goggles use yellow/orange to reduce glare

Here are some comparison shots I found on google
http://km33.com/index.php/phototech/651-explaining-filters.html

I don't have the glasses on me, they are in another car. I will try and stick these infront of a cam and go for a drive tonight

It might not be the answer, but maybe a Cpl filter used with a yellow filter will mean you can use it 100% of the time.
 

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