Dahua 4MP 25mm LPR Modification

[ldasilva]

that should be nice
i have a DS-2CD2035-I i installed like 1 year ago with 12mm lens which isnt close enough only works maybe 30% of the time at the time i ordered a 25mm lens to replace the 12mm but i never installed it

 

[ldasilva]

wow

 

[nayr]

after focusing this at night, daytime still looks perfectly fine.. just a lil fuzz


So the lesson here is you need test plates, and you needa focus it at night on your test plates for best results..

 

[ldasilva]

after focusing this at night, daytime still looks perfectly fine.. just a lil fuzz
View attachment 14433

So the lesson here is you need test plates, and you needa focus it at night on your test plates for best results..

test plates makes it so much easyer
pain in butt to wait for cars to passby

 

[nayr]

i admit it was quite a bit trickier to focus on a plate with high zoom at night.. had to plug the faceplate back in and hook the IR up.. and then of course as your adjusting the focus the plate is bouncing about and requires you to sit it all back down and scrutinize the video on a solid surface.. then repeat.. at least with manual varifocal cameras they can be mounted/fixed while you focus it.. pro-tip, use a small table/chair/something that you can turn the whole damn thing to point it back at your target without fiddling w/the sensor..

but yeah; if you want a LPR camera.. you need test plates, or else your going to spend weeks dicking with it instead of getting it done in a night... rarely will a car stop in the perfect spot and pose for you.

Worst case steal the plates off your own cars and make a prop out of cardboard so if anyone runs it over it wont damage there car or your plate.. also gotta wait for traffic to get rare enough you can leave a plate in the road for 10mins or so w/out anyone hitting it.

 

[ldasilva]

good tips
will help speed install a lot faster for ppl wanting to do it

 

[bug99]

this is cool. it appears to me that in all images that you prioritized focus on the left plate over the right one, which is slightly further away. also it also appears that you could drop the sharpness down a few points to reduce the over-blur (its backwards that way) a tinny bit. overall a good image in both lighting conditions and a vast improvement over the 12mm.

if instead of focusing the camera at night with the lens, you instead moved the chair, how far do you think the chair needed to move to get perfect focus over the day image?

 

[nayr]

no, both plates are equal distance away.. one is just very old and the other is very new, gotta compromise on settings to find an exposure that leaves the old less reflective plate legible without over-exposing out the brand new very reflective plate.. the more reflective the target the closer it appears, and thats why the focal points all change once the IR flares the plates up.

I focused the camera on my lil foot stool out my backdoor, I didnt move it closer.. after turning the barrel and putting the camera back down on the stool it almost never had the plate in frame because i had digital zoom cranked way up.. so id just turn the stool til it came back into view, take a snapshot and flip back and forth with my previous snapshot to see if focus was better/worse, kinda like your optician does w/those big lens rigs.. then repeated until I had everything dialed in.. The thing is you cant hold the barrel in your hands and adjust the focus the same time with this level of zoom.. image is far too unstable to see if your focused or not and everything is black except the plate.. my pinwheel target was entirely useless for this exercise.

then i put it back together and took it back outside, attached it to my wall where it was before and took these captures.

sharpness already been reduced a few points, if I move it anymore it hurts the legibility of the plates.

 

[nayr]

realized I been cropping all these plates and nobody has an idea of the entire FOV, attached is a full uncompressed image.


Quick estimation is about ~20ft wide at the fence if I counted the planks right

 

[ldasilva]

realized I been cropping all these plates and nobody has an idea of the entire FOV, attached is a full uncompressed image.
View attachment 14437

that looks good i think a 25mm might be enough for my 2 roads

 

[bp2008]

Mjpeg doesn't work beyond 1080p? If you have the CPU available, you could probably get ffmpeg or VLC to convert h.264 to mjpeg for you. Not sure it would be reliable though without a watchdog script.

 

[nayr]

nope not on this camera; works fine on the 4MP Varifocal Bullet and my 4MP Bullet-Box... but not this cheap ass Chinese model.. the SOC on this camera is weak as Steven Hawking, I can do MJPEG in up to 28Mbps bitrate and full FPS on the other cameras, but this one can only do 1080p and a fraction of the bitrate (11Mbps)

 

[bp2008]

Kind of like my Dahua 12x PTZ (years old now) which has laggy PTZ input if I stream H.264 at full frame rate / bit rate...

The whole web server lags on that one if the encoding is too intense for it.

 

[nayr]

yeah my black face 12x ptz has same problem, at full bitrate it laggs like motherfucker.. knock it down just a couple Mbps and all is fine again.

cant wait to get my hands on a 25x Starlight; with intelligent support they added alot more muscle under the hood.. the Arm v7 came out since that camera was released and the v6 was pretty pathetic in comparison.

 

[nayr]

started snowing a bit and since the cameras on test rig are not sealed off cabling I unplugged em and brought em back inside.. fixed the LPR camera in the living room looking out the window at the same distance im looking at for mounting.. luckily had some traffic quickly, this is gonna get the job done.



its nice not shooting as far as my other LPR camera w/60mm lens.. the focal plane is much larger and the background houses are alot more in-focus.

 

[weigle2]

One thing I learned when working security at a large company. All anyone needs to do to eliminate their plate being read by almost any camera, is cover it with a polarized or smoked plastic cover. Unless you are looking dead-on at the plate, it's not readable. This technique is also useable on the Tollway lanes for those that refuse to pay tolls.

 

[hmjgriffon]

One thing I learned when working security at a large company. All anyone needs to do to eliminate their plate being read by almost any camera, is cover it with a polarized or smoked plastic cover. Unless you are looking dead-on at the plate, it's not readable. This technique is also useable on the Tollway lanes for those that refuse to pay tolls.

thanks for the tip bro, gonna do some experimenting lol.

 

[nayr]

One thing I learned when working security at a large company. All anyone needs to do to eliminate their plate being read by almost any camera, is cover it with a polarized or smoked plastic cover. Unless you are looking dead-on at the plate, it's not readable. This technique is also useable on the Tollway lanes for those that refuse to pay tolls.

A few people have those in the neighborhood, they dont work as well as you'd think.. they are perfectly readable in the daytime at least on my cameras but they are pretty much head on, at night they are usually not bright enough to be automatically read but I can get a good idea to search through my daytime captures.. If you had a visible light flash like most of the red-light cameras arround here I think the'd be defeated there too.

also they are illegal here, and if you park on the street anywhere in metro meter-maids will nail yer ass in a heartbeat; they utilize mobile plate readers and scrutinize any unreadable vehicles.. watch people get nailed downtown all the time for minor plate issues, even as simple as having the sticker on the wrong side.

 

[Kawboy12R]

They don't enforce plate fudgers here. Pet peeve of mine. Tons of plate masks installed but there's no will to enforce.

 

[nayr]

be careful what you wish for; likely the only reason we enforce it here is because of all our damn traffic cameras are too lucrative of an income.

LPR is never 100%, far more common than plate fudgers are:

• Trailer Hitches
• Work Truck & Trailers with Heavily Damaged Plates
• People whom havent ever once been to a carwash, or
• Coated with winter road grime
• Bike Racks
• Original Owners of old vehicles with original plates (Colorado thing) that long ago stoped being reflective
• Cargo Boxes/WheelChairs
• Big Ass Spare tire for Jacked up Truck/Jeep
• Temporary Tags
• Motorcycle hauling ass

but ive already had several instances where having a legible plate image would have been a game changer, its definitely worth attempting IMHO