LPR - focal length and sensor size

[saltwater]

I already have 11 cameras covering my property, 9 are @EMPIRETECANDY (Andy) supplied 5442's and very happy with them.

I like the larger sensor size of the 5442 but now I'm looking at purchasing two LPR cameras. From my understanding, a 2 mp camera, zoomed in (most likely a variable focal model) will do the job. I do realize the larger the sensor sizes the better the clarity of the video/image, but for LPR purposes is it a factor to take into consideration? Most of the specs I read for the 2 mp variable focal versions are 1/2.8 inch. At this stage, I'm not overly concerned with Deepstack or something similar but hopefully that's not a factor should I decided to dabble with Deepstack once things are set up.

My LPR will more or less have direct head-on view of approaching and leaving cars, both front and rear plates. They will be installed in my letterbox about 900 - 1000 mm high, along side two 5442's for general overview, or slightly wider view of the road.

 

[wittaj]

2MP is more than enough for LPR. Focal length, distance to plate, and shutter speed are more important. Heck I have an old analog camera at 720P that works just fine, and OpenALPR recommends 720P in some instances.

The biggest thing we see is people always underestimate the actual distance. 50 feet turns out to be 75 feet and then the camera selected isn't the right one.

The Z12E is capable of reasonable distances of 150 feet, but people have been able to get it to 220 feet, especially with additional IR.

The Z4E is the next camera that people have tried, but most have found beyond 50 feet, it is difficult to make out the plates because the optical zoom of that camera is half of the Z12E optical zoom.

After that, it would be one of the varifocal turrets, but those will only reach about 30 feet, but do work well on a mailbox at the street. About half the price of the Z12E.

The Z12E and Z4E are the same price, so between the two, why not buy the one that provides the best opportunity to get a longer distance if needed.

During daytime it may act as an overview, but at night the shutter tends to need to be faster to capture the plate, and the faster the shutter, the darker the image.

Most of us run B/W to take advantage of the reflective properties of a plate which is why we can run a faster shutter to get the plates. Once you decide to keep it in color, the shutter speed slows way down and might not be fast enough to actually capture a plate.

At night, we have to run a very fast shutter speed (1/2,000) and in B/W with IR and the image will be black. All you will see are head/tail lights and the plate. Some people can get away with color if they have enough street lights, but most of us cannot. Here is a representative sample of plates I get at night of vehicles traveling about 45MPH at 175 feet from my 2MP camera (that is all that is needed for plates):

However, for a camera on the mailbox that is next to the side of the road and could be getting the front or back of plates within 30ish feet or so, then the 5442-ZE varifocal turret will work:

https://www.amazon.com/EmpireTech-IPC-T5442T-ZE-Vari-Focal-Eyeball-Starlight/dp/B08C77TNY9/ref=sr_1_1?dchild=1&m=A329YQ83EBQGJF&marketplaceID=ATVPDKIKX0DER&qid=1625601227&redirect=true&s=merchant-items&sr=1-1

As will the 2MP T2231T-ZS that is a lot cheaper:

Amazon.com : Loryta IPC-T2231T-ZS 2MP Starlight WDR IR Eyeball Network Camera Motorized Vari-Focal 2.7mm–13.5mm Lens English Version
Amazon.com : Loryta IPC-T2231T-ZS 2MP Starlight WDR IR Eyeball Network Camera Motorized Vari-Focal 2.7mm–13.5mm Lens English Version
www.amazon.com

 

[richardgohth]

If only want to capture retro-reflective plates, any sensor is fine.
Non retro-reflective plates requires much more sensitivity at night and requires
mono sensors with NIR lighting.

 

[saltwater]

Thanks all for the info.

From one direction, a bend is about 50m (164') away and as a car drives past the letterbox, it's only between 3 - 6m (10 - 20') away, but that's directly side-on and no plate visible. From the other direction the cars will approach from 200m (650 ') away. With all that said, I should have a good sweet spot somewhere in between.

 

[wittaj]

Yeah, you will need to pick the spot to focus on distance-wise and get the right camera.

Once you zoom in, the focus is tight and depth of focus for the frame is such that all but the "Sweet Spot" will be soft out of focus.

 

[samplenhold]

At 164' you are approaching the limit of the 5241 Z12E that most here are using for LPR. Now a few have used it out to 200'+, but 600' is a non-starter.

Here are a couple of threads that discuss LPR setups.

New to LPR? Considerations Before You Begin

Thought I would throw together a post on my experiences so far with LPR in an effort to help others that are considering running down that rabbit hole. There are some practical considerations you should know about LPR. I am approaching this from the position of using Blue Iris and Plate...

ipcamtalk.com

LPR Case Study: Scoping, Planning, Proof of Concept, Installation, & Results

Introduction This thread is about my journey into LPR (License Plate Recognition) after having about 18 months of experience with IP cams and having quite a bit of my system finished. I am not an expert on LPR, or IP cameras either. But I have spent a lot of time working with my system and...

ipcamtalk.com

 

[saltwater]

At 164' you are approaching the limit of the 5241 Z12E that most here are using for LPR. Now a few have used it out to 200'+, but 600' is a non-starter.

Here are a couple of threads that discuss LPR setups.

New to LPR? Considerations Before You Begin

Thought I would throw together a post on my experiences so far with LPR in an effort to help others that are considering running down that rabbit hole. There are some practical considerations you should know about LPR. I am approaching this from the position of using Blue Iris and Plate...

ipcamtalk.com

LPR Case Study: Scoping, Planning, Proof of Concept, Installation, & Results

Introduction This thread is about my journey into LPR (License Plate Recognition) after having about 18 months of experience with IP cams and having quite a bit of my system finished. I am not an expert on LPR, or IP cameras either. But I have spent a lot of time working with my system and...

ipcamtalk.com

That distance is where the other bend/corner is, never intended to attempt LPR at that distance. From that distance, the cars get closer, so I will pick a distance of around 15-20m. An advantage I have is that if one LPR camera misses, there's a good chance the other LPR will pick up. Here in Australia, it's a requirement for both front and rear plates.

 

[EMPIRETECANDY]

15-20m, the IPC-B5442E-Z4E can do the job.