New to LPR? Considerations Before You Begin

David L

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Your FOV is really three lanes wide. So that is really 36 feet wide. As @DLONG2 stated, get closer and not worry about the gutters. No plates will be in that area.
Funny until I read the last part of your sentence, I had Roof gutters in mind, thinking they must hang down a lot to get in the way of the CAM, LOL...
 

pbc

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Weird. Went out a couple nights ago and sat in the road focusing on my plate with 1/1000 exposure, 50 HLC. Everything looked great. But capturing way less now with blurry plates unless they are fully stopped at the stop sign. Reducing FPS the cause? I.e, wouldn't more frames per second give a better chance of capturing plates?

Figure it's that, or moving from 1/500 to 1/1000. Maybe given the size of the road I'm capturing 1/500 works better for whatever reason?
 

bigredfish

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Going to a faster shutter will make it a bit darker, but not more blurry. Opposite actually.

And FPS has nothing to do with focus. I argue more FPS helps in LPR just because you get more frames to pick from to get the best image, but this isn’t your problem.

Did you change anything else?
What are your DNR settings?
Is the plate well lit but blurry?
 

wittaj

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Yep FPS has nothing to do with blurry....well in some instances if you are maxing out all the specs in the camera then a higher FPS can result in blurry images but that is because of the camera not being able to keep up with the shutter speed and other parameters and results indirectly in blurry images.

Did you write down the focus number and are sure that it is the same focus number now? You could have set it a few nights ago and now it focused on something else and the focus number is different (we see that here all the time).

Post pics of your other settings, along with the zoom focus number (how far zoomed in is it). As this thread shows, things like gamma, brightness, contrast, etc. impact focus as well (which most people would not think it would).

 
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wittaj

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And on the other end of the FPS spectrum LOL:

Here is a representative sample of plates I get at night with a 1/2,000 shutter and 8 FPS of vehicles traveling about 30MPH at 175 feet from my Z12E that is on the 2nd story soffit, Camera is 35 feet above street at this location with no street lights or house lights on, just the infrared from the camera:

1674173348880.png

The vehicles are in and out of my field of view around 0.5 seconds, so I am getting 4 or so frames per plate and get them all, except for the rusty or dirty or bent or temp or any other plate that wouldn't be captured anyway.

I run it low because I use OpenALPR and that thing is a resource hog and 30FPS would bring my system to its knees. 15FPS is even a struggle for it. As long as I get the plate, that is all I care about.
 
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pbc

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Anything stand out in the above? One issue I noticed is I had a mismatch on frame rate between BI and the cam so not sure if that was causing the blurring on moving plates (though they are not moving very fast there).
 

wittaj

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No those seem reasonable.

I still think it is a focus issue and you set it at one number and a couple days later it is off a few.

OR you are zoomed in so tight that the focus depth is so tight that anything before or after that is blurry. Maybe try bring the iris down as a higher iris setting can shrink the available area of focus.
 

pbc

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Just getting back from an overseas trip. Here's an example of the blurriness I'm referring to other than when the car is completely stopped (even then not as focused so will need to work on that).

 

wittaj

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Just getting back from an overseas trip. Here's an example of the blurriness I'm referring to other than when the car is completely stopped (even then not as focused so will need to work on that).

OK a lot going on there and I don't think you provided yet how zoomed in it is, but the closer you get to max zoom, the smaller the focus area is.

The blurry when the car first enters is due to being off-center of the infrared. Infrared works be reflecting back, so when it off the center, it has trouble reflecting back. That and that isn't the focus point I suspect.

1674613698628.png

Now the plate starts to get readable as it gets more centered and closer.

1674613783312.png

This is probably the cleanest shot.

1674613824997.png


I suggest you have someone go out and stop at say those three locations and then focus and you will see the focus number will be different for each one.

You then need to decide which one is the one you want to get the clean focus or average the focus numbers of the 3 spots and then recognize it won't be clean and crisp everywhere, but may be readable from more distances.

Even with my tight image where a car is in and out of the frame in under 0.5 seconds, as it gets close to and outside the red box, it gets blurry. The focus numbers starting top right corner to center to bottom left corner were different by 10 steps. So I went with the clear focus step in the center and can still read the plates outside of that, but they will be a little blurry.

1674614092974.png
 
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