Number plate readability - typical distances?

Rajagra

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Dash Cam
Mini0806
I've been reading some of the threads about having to refocus the lens on some dashcams. It made me wonder if mine needed doing. Checking my videos it's a bit disappointing that plates more than what seems like 2 or 3 car lengths away can't be read. If refocusing needs doing, I'll do it. But I don't want to rip it open unless it's necessary.

Is there a table of how far away various dashcams should be able to read number plates? I know there are many variables in play, but surely they can be dealt with.
I did some tests on my Mini0806 with custom bitrate firmware, at 2560x1080 30fps superfine.
Summary of results looking at my UK white front numberplate at key distances, hand holding the dashcam.
Late afternoon, cloudy but fairly bright, even light:

11m: Very readable. (White part of number plate takes up 62x15 pixels.)
14m: Quite readable, but starting to need to guess some characters. (49x11 px)
17m: Unreadable. (40x10 px)

So a little better than I thought it was, but maybe possible to get more out of it?
How does this compare to other 0806s/other dashcams?

NB UK law requires drivers to be able to read number plates at 20m, so my camera fails that test! :D

UK number plate specs:
Characters must be 79mm tall
Characters (except the number 1 or letter I) must be 50mm wide
The character stroke (the thickness of the black print) must be 14mm
The space between characters must be 11mm
The space between the age identifier and the random letters must be 33mm
The margins at the top, bottom and side of the plate must be 11mm
Vertical space between the age identifier and the random numbers must be 19mm
 
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Good question and I hope some knowledgeable person jumps in. I have just (1 month now) bought a BlackVue DR650 1Ch and am disappointing with the clarity of the video. I also wonder about out of focus.. and, what the criteria is. I have found it "reasonable" if stopped and the car in front is stopped as well, but while driving at 80 km/ph with a car overtaking me, and staying in the adjacent left lane.. at no point is the plate readable.
 
1080P resolution paired with a wide angle lens can only do so much. it doesn't matter how much you've spent on your camera. dash cams are wide angle so they can capture much of the scene around you while sacrificing the details. if you need the plate number of the person in front of you, make sure you have audio recording on and read it aloud.

it seems folks have waaaaaay too high of an expectation about what 1080p can do. the only way that 1080 can capture plates 3-4 cars ahead is if you have a narrower field of view on your camera.
 
Good question and I hope some knowledgeable person jumps in. I have just (1 month now) bought a BlackVue DR650 1Ch and am disappointing with the clarity of the video.
as are most. get the custom firmware, that improves it a bit if you don't want to dump it for a cheaper better camera.
 
There is lots of mention of "custom" firmware.. but no links to.. or benefits /description of, that custom firmware.
 
Thanks for the link.. unfortunately the little Russian I learned in school is not up to the task now 50 years later. Has anyone used this software on the DR650 1Ch. But, the bigger concern is it reversible.. There is also occasional mention of a "donation". I am all up for paying for better firmware.. but.
 
the wider the field of view the shorter the focal sweet spot
So how does that work if you can change the view angle. Example Joovuu X camera. Focus is at the same spot.
Will you get the same amount of pixel density in the two photo. so you won't gain anything, when you zoom in?
 
So how does that work if you can change the view angle. Example Joovuu X camera. Focus is at the same spot.
Will you get the same amount of pixel density in the two photo. so you won't gain anything, when you zoom in?

I've no idea how it's going to work with the joovuu x. the ideal way to change FOV would be with a different lens. if FOV changes are done via software, you're definitely talking about digital zoom which will drastically reduce quality using pixel doubling. I very much doubt we'll be seeing optical zoom lenses on dashcam with all the space and monetary restraints.
 
FOV changes are done via software, you're definitely talking about digital zoom which will drastically reduce quality using pixel doubling.
So no gain, just more software programming = more expensive product.:( I guess it most likely will be a use-less function.
 
So no gain, just more software programming = more expensive product.:( I guess it most likely will be a use-less function.

if I have to guess, different FOV lenses will be available much like the mobius. that would be both cost effective and it keeps the picture quality intact.
 
So how does that work if you can change the view angle...

I don't know how JooVuu X does it, but each Mobius lens offers a user-selectable choice (via GUI) of 3 FOVs...

1080p/30fps. Wide Mode. Captured from 2304 x 1296 CMOS pixel array & scaled down to fit the 1920 x 1080 frame size.

1080p/30fps. Narrow Mode. Captured from central 1920 x 1080 CMOS pixel array. There is no scaling of the image.

720p/60fps. Captured from central 1280 x 720 pixel array. No scaling of the image.
 
yes, of course. scaling. i forgot about that. makes a lot of sense.
 
@Ralph2
At "car-dvr.info in the top box, look at the lower right corner; clicking the 'Union Jack' icon will get you an English translation. A few words and phrases don't come through but you can still understand what's going on.

Phil
 
Thanks for the link.. unfortunately the little Russian I learned in school is not up to the task now 50 years later. Has anyone used this software on the DR650 1Ch. But, the bigger concern is it reversible.. There is also occasional mention of a "donation". I am all up for paying for better firmware.. but.

@alexsoll is the best one to answer your questions
 
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