Reading number plates. How far, what resolution and what lens?

[cosmo]

Does anyone have a chart cross referencing the readibility of a car number plate based on these three parameters?

The assumption is that the car is stationary. And of course I can't imagine being able to read a plate at night with IR unless it is a very targeted lens and close. Or I could be mistaken...

I tried to pick a lens based upon what I thought would be enough but in the end just bought a 2.8-12mm to experiment. But I'm interested if anyone has experience.

 

[SyconsciousAu]

Readability of a plate is all about the pixels per metre. You can do it with a D1 resolution camera if you have enough zoom. I use a 12.5-50mm lens but if the camera is close enough to the plate, you will still get the required ppm. I have a sub $50 illuminator doing night duty and run 1/1000s shutter.

 

[Kawboy12R]

Use the IPVM.com calculator for a decent ballpark. For the 1/3" Hiks, when I plug in a 2.5" sensor size (my particular Hiks weren't in their select-a-cam section) it fairly closely matches the real world FOV. Other folks have disassembled Hiks and measured the sensor and say it's really a 1/2.5". Then, when you fiddle with the adjustable cone it gives you, figure on at least 30 ppf as a semireliable minimum figure in unchallenging lighting to read a plate with your eyes at a bit of an angle in the daytime. 35 is better and there are also other factors involved even in daytime like movement, uneven lighting, shutter speed, etc. A shadowed plate in sunlight can be unreadable in the same spot where it is fine on a cloudy day.

My 3345-I 4mp turret with 6mm lens can capture a stationary plate at over 80ft at a moderate angle (20 degrees?) on a cloudy day but it's not even close at the same spot in the shade when it is sunny.

You have to ground truth the IPVM calculator with the cam or family of cams you want to use it with though. Your cam won't necessarily have what the published specs says it has. For an addon varifocal lens, mount the cam outside and shorten it to the minimum lens length. Then, in the calculator, after plugging in what the camera specs told you, adjust the sensor size value until the calculator's estimated view matches what the camera really sees. Then when you change the length in the calculator you can drag the FOV cone around and judge where you get at least 30-35 ppf for eyeball plate reading in decent daylight conditions. For clear faces, try for over 100.

 

[pozzello]

I'm getting plates at night on moving vehicles (20-30mph) from about 60ft with husun/imporx miniptz:

It's a 1080p cam with 5.1-50mm lens for 10x zoom. I'm using almost all of it (~9x)
of course, for this to work, the settings are such that I don't see much other than plates & head/tailights at night (1/1000 exposure)

 

[nayr]

This calculator is pretty useful, dunno how accurate it is but it should give you some ideas: https://www.anpronline.net/calculator.html

 

[SyconsciousAu]

judge where you get at least 30-35 ppf for eyeball plate reading in decent daylight conditions. For clear faces, try for over 100.

Thats only 100 - 120 pixels per metre and you would struggle with plates at that resolution in Australia. Digits on local front plates are only 50mm (2") high. Australian Standard for plate recognition is 410ppm but in testing I could get away with reliable human recognition at 200ppm.

 

[cosmo]

Australia. Land of speed cameras. Everywhere. On every freeway. In suburban streets. A facist's wet dream. Ask me how? 30 years living there.

2mph over the limit and a camera will mail a $185 police invoice to your home. 6mph: $295. 15mph: $406. And it goes on. They're subcontracted to private companies. No review board. Not even a real court. Pay or you're hosed. Apathy. And a lot of it due to number plate recognition technology.

http://www.abcdiamond.com/australia/speeding-penalties-in-australia/

https://www.vicroads.vic.gov.au/registration/new-registration/registration-labels

"How will the Police identify if a vehicle is registered without the sticker?"

Most police vehicles have online access to registration data through their in-car mobile data terminals.

The use of Automated Number Plate Recognition technology also means that Victoria Police can easily scan traffic and identify which vehicles are unregistered.

Just because a vehicle has a registration sticker on the windscreen doesn’t mean it is registered, as that sticker is sent out regardless of whether the registration is paid.

 

[SyconsciousAu]

That was random.

 

[klasipca]

Australia. Land of speed cameras. Everywhere. On every freeway. In suburban streets. A facist's wet dream. Ask me how? 30 years living there.

2mph over the limit and a camera will mail a $185 police invoice to your home.

This is excessive! Is everyone driving under speed limit then?

 

[cosmo]

This is excessive! Is everyone driving under speed limit then?

Pretty much. The fines are high and there is no leniency, so everyone sticks right to the speed limit and in many cases a few kph under to be safe. Initially the government made a fortune, but when people started to all drive at the speed limit, the revenue dropped, so then the government took another, sneakier, even more draconian tactic: They started reducing the speed limits everywhere around the state. Country roads that for decades used to be 100kph (60mph) suddenly went down to 90. That would catch a few more people. 80 zones went to 70. Some roads would change from 80 to 60 then back up to 80 for no apparent reason. Any time there is construction, which is all the time on major roads, the speed would go down from 100 to 80 or 60 for miles, even if there was no construction crew there (Which is not legal BTW), and they'd stick a speed camera in place to nab the offenders.

It is OUT...OF...CONTROL.

But Aussies are a apathetic lot on this subject and nobody has raised it to the point of being a political issue.

An example: The South Eastern Freeway out of Melbourne is 10 lanes across in one part. It's a freeway. No traffic lights, no intersecting or merging roads in this section. But the speed limit goes down from 100 to 80 all the way, 24 x 7. And there are cameras there that bring in a fortune. I think to the tune of $900 million a year last year. The third single biggest revenue raiser for the state behind property and payroll taxes.

Many inner city roads have 40kph (25mph) sections for miles at a time.

The worst part is that drivers stay in the fast lane and won't move over.

I couldn't wait to get back to California, where the general rule on speeding is "just don't pass a cop that is".

 

[Kawboy12R]

I bet those gps apps that mark where speed cameras are are pretty popular. I'd change my warning to say "Start wheelie now" and flip the cam the bird as I passed. I wouldn't have a big problem with them if they were set to 5 or 10 over.

 

[cosmo]

I bet those gps apps that mark where speed cameras are are pretty popular. I'd change my warning to say "Start wheelie now" and flip the cam the bird as I passed. I wouldn't have a big problem with them if they were set to 5 or 10 over.

Maybe, but that won't help you.

They have lots of contractors on the side of the road in unmarked cars of all types, usually with tinted windows. The driver sits in the passenger seat with the seat reclined, probably asleep. On the dash there's a speed camera that captures your plate when you go by, uses OCR and two weeks later you get an invoice from Victoria Police to pay up or go to court. If you want to see the photographic evidence, you have to either pay for a copy of the photo to be sent or drive into the city police headquarters and stand in line to view it.

Even if you know where some of the cameras are, slowing down to pass them won't always work. On lots of the freeways they have point to point cameras that not only record your speed and registration number, but they time you to cameras further up the road. If your point to point time is less than the time it would take to get from point to point at the maximum permissible speed, you'll still get fined and they just average the speed.

You can't win. The only solution is to register camerasmashers.com and start a movement where people can send in their photos of them destroying speed cameras, purely for the delight of the general public and to send a message to the government. Buty of course, they don't care, would just charge the taxpayer and the camera company makes out twice!

 

[nayr]

sounds like you dont have any more cops on the roads with all those cameras and traps, so just toss your license plates in the rubbish bins and speed to your hearts content..

or get a big white magnet and slap it over em so you can still park intown without getitng nicked.

 

[klasipca]

Here is a solution

 

[cosmo]

Here is a solution

Yeah, I've seen them all.

At first, it was plates with bubble plexiglass over them. It was quickly discovered that the flash on speed cameras would reflect off the plexiglass. They were quickly made illegal and if a cop saw one on your car, he would pull you up and issue a hefty fine.

Then there's all these devices that flip the plate up/down. That's fine if you know where the camera is, but otherwise won't help. And if you just drive around with the plate flipped down, you'll draw attention to yourself, and definitely the cops.

The digital plates - also, if a cop sees it, they'll pull you over.

What I thought was brilliant was the inconspicuous plate flipper that has your normal plate on one side and some other plate on the other side. Even when you've got the other plate showing, nobody would notice that anything's wrong.


Personally, I'd like a number plate made with the letters of some VicRoads government official's wife's car, then speed around and have them deal with all the paperwork of proving it wasn't them.

Better still, drive the same make, model and color of the husband's car and blow some red light cameras at 2 in the morning in the city's red light hooker district. Imagine the husband/wife discussion.

 

[Kawboy12R]

It might be funny to pick a speedcam bigwig and do it wearing a Guy Fawkes mask and have your girlfriend or perhaps a real working girl beside you.

Lots of people here have semi-opaque plate covers but they're mostly to keep the cellphone brigade from getting a good look at your plate when you blow by. There's little or no will to ticket people just for those plate covers either.