Which covers have you noticed are able to defeat your LPR?

[Ri22o]

Other than the 3M plates, I have noticed that there are some plates that my camera has a hard time picking up. What have you all found/noticed in your LPR captures that prevents your camera from getting a good OCR?

I am also seeing more and more Flock systems in my area and am curious how well these handle various covers or deep grey area attempts at avoiding legible captures.

 

[wittaj]

Paper temp tags are tough. Dirty plates are tough. Any of the plastic covers can be problematic at night. Some states those are illegal, but nobody enforces it.

My friend is a police chief where they have Flock systems and he says my cams are better at picking up plates LOL.

 

[Parley]

California has a vanity plate with a black background and yellow/orange lettering. So far those are the hardest to read, but the addition of an IR illuminator has helped in my situation. I cannot say that the IR illuminator works for everyone. I went from no way can I read that, to a chance by going frame by frame. Here is one on the front of a car with the headlights on from last night. The plate number is BZ30T94. Going frame by frame helped with this one. Notice that the colors are switched by the camera.

 

[Timokreon]

Seems like quite a few of the license plate covers presents problems at night.
I'm still attempting to get color 24/7 on my 437. Mainly because of false readings when it rains, but the covers and new plates are becoming more problematic by the month.

 

[Flintstone61]

I have one neighbor in the Apartments with a smoked plate cover. I can't make out the numbers with any certainty. But I have gotten him during the day.....

 

[Flintstone61]

In a previous Catalytic converter crime. The red Mazda involved in the crime, came thru a couple times in the days leading up to the crime, with no Smoked plate covers...I saved his plate because his behavior was uncharacteristic of a resident or a guest.
On converter theft day he had applied the covers but I already had him.
The police were able to get a suspect name of the car owner. and he was " known to Law enforcement".

 

[Parley]

With my LPR system I can get the front and back of every vehicle that goes by. What I have found in a lot of cases is that someone goes to a lot of trouble to make the rear plate unreadable, but they do nothing to the front plate. So, I can get that one. Now for those vehicles that do not have a front plate then I cannot get those. However, those cases are in the minority. I would have to say that I get around 98% of the plates now that I have relocated a couple of cameras to the tree in my front yard and have added the IR illuminators. One recently, I had to go frame by frame on both the front and back plate to get the reading.

 

[Parley]

Other than the 3M plates, I have noticed that there are some plates that my camera has a hard time picking up. What have you all found/noticed in your LPR captures that prevents your camera from getting a good OCR?

I am also seeing more and more Flock systems in my area and am curious how well these handle various covers or deep grey area attempts at avoiding legible captures.

Do you have any pictures of the plates that you are talking about?

 

[Ri22o]

Do you have any pictures of the plates that you are talking about?

I don't check too often and would need to dig through, but when I was going through the settings and checking more frequnetly I noticed I had some cars that would come through with tinted covers that were sometimes difficult to make out the plate numbers.

 

[Parley]

By the way, here is a photo of the standard California plate in about the same position as the one in the photo above for comparison. Post #3.

 

[Parley]

Here is a good example from last night of someone dirtying up their plates. This car passes two of my LPR cameras, so I got the front and rear 2 times. Now LP3 is the one with the extra external IR. The plate number is 6YTN887.

Here is the two pictures from LP3 with the extra IR illuminator.





Now the two pictures from LP4 without the extra IR illuminator.

 

[samplenhold]

I read an article about some people in NYC that cover their plates with masking tape or change the number with electrical tape. They do this to defeat the tolls.

 

[Parley]

I have noticed that there are a few people in my neighborhood who have sprayed something on their plates to make them non-reflective. I have only seen a couple of cars with a "clear" plastic cover. Here is an article on how to make your license plate non-reflective. However, I am still able to get most of those like the photos in thread 11 show.

How to Make Your License Plate Invisible to Cameras | WinIt App (appwinit.com)

 

[jec6613]

I read an article about some people in NYC that cover their plates with masking tape or change the number with electrical tape. They do this to defeat the tolls.

This only works at the older gates, modern gates are using effectively a DSLR in a housing with a proper flashgun - they get you every time.

 

[samplenhold]

This only works at the older gates, modern gates are using effectively a DSLR in a housing with a proper flashgun - they get you every time.

Not sure how the flashgun or DSLR in a housing would pull off electrical tape from the plate.

 

[jec6613]

Not sure how the flashgun or DSLR in a housing would pull off electrical tape from the plate.

You don't have to, the computer just has to flag it as suspicious for a human to look at it, and they can recognize it as electrical tape and the shape underneath it.

Edit: I should mention that there's a huge chasm between the performance of a typical LPR camera, and an ILC set for trap focus at a toll gantry, and it's all about the data coming in and how it's stored. The biggest sensors available are about on a PoE camera 4/3" with 225 sq mm of capture area with slow shutter speeds, and new gantries are using 864 sq mm sensors (36x24 full frame) at either 24, 36, or 45 MP, with a macro lens and shooting at 1/250 or higher with flash exposure time of around 1/4000, and do so 100% of the time with enough exposure latitude to recover an image that's otherwise exposed as perfectly black*. And then you still have the typical LPR camera pair (front and back) that handle most cases where you don't need the high res image. The LPRs will flag for things like a non-reflective portion of the plate, and so on, and when required, the high res image is pulled and it's trivial to tell electrical tape apart from the actual numbers on the plate, and recover the info through any plate cover.

And why, you ask, would they spend so much on camera equipment for a toll gantry? Well, because around NYC, a $15 toll is not unusual.

*Exposure latitude and recoverable detail correlates directly to sensor size, assuming you're capturing in a raw or near-raw format. A typical FF sensor will have 14+ stops of dynamic range, a 4/3" sensor 12 stops, and a typical good low light camera suggested around here (1/2.5-2.8" or so) around 8 stops. This means a modern toll gantry stills camera has 64 times (at least) the available data. And that's before any sort of video compression to mush it down further, while typical still image sizes are ~40 MB.

One further edit: the new toll gantry still cameras can also read your under-glass VIN as well in some cases. There's four pixels per square mm if set up correctly, or an entire Bayer pattern worth.

 

[bigredfish]

I've seen this before down at my previous home in Orange County.

Its obviously some type of stuff the smear on the plate. The others were similar, looked like it was applied with a brush or something. Not all have it, i think its a "non-offcial" individual officer thing

 

[Parley]

When I walk around the neighborhood, I can see the plates that have had a non-reflective substance applied to them. Either sprayed or brushed on. I know of two cars that have a clear plastic cover over the rear plate. However with the extra IR I am now able to read those plates. Not sure about the ones with the plastic cover.

 

[Timokreon]

There are more vehicles every day that no longer have front plates, even though it's illegal not to have them. Along with no longer having front plates, a LOT of people are using the plastic (or whatever it is) coverings for their rear plates.
Or using a clear spray.

I really need to start experimenting with my 5241, or get the new one, to see if I can get it to run 24/7 color.

 

[Mike A.]

Kind of interesting I thought... Lately I've seen multiple cars with their plates turned upside down. I'm wondering if it's an attempt to foil readers while still meeting plate display requirements. I looked at the regulations here and while it has the usual prohibitions against altering or obscuring plates, it says nothing specifically about them being turned the right way.

§ 46.2-716. How license plates fastened to vehicle; altering appearance of license plates.
A. Every license plate shall be securely fastened to the motor vehicle, trailer, or semitrailer to which it is assigned:

1. So as to prevent the plate from swinging,

2. In a position to be clearly visible, and

3. In a condition to be clearly legible.

B. No colored glass, colored plastic, bracket, holder, mounting, frame, or any other type of covering shall be placed, mounted, or installed on, around, or over any license plate if such glass, plastic, bracket, holder, mounting, frame, or other type of covering in any way alters or obscures (i) the alpha-numeric information, (ii) the color of the license plate, (iii) the name or abbreviated name of the state wherein the vehicle is registered, or (iv) any character or characters, decal, stamp, or other device indicating the month or year in which the vehicle's registration expires. No insignia, emblems, or trailer hitches or couplings shall be mounted in such a way as to hide or obscure any portion of the license plate or render any portion of the license plate illegible.