140* FOV on A129 Duo rear-cam not wide enough

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I have the rear cam placed on the rear windshield of a compact sedan. Something like a Honda Civic size. To my dismay, I found that the 140* FOV does not cover the whole windshield width.

I never tested the coverage before until recently. When I stand near the side of rear windshield whereit meets the pillars of the car, the rear cam can't see me. Two obvious reasons. 140* FOV and the rear cam is almost flush on the rear windshield. I would need a 170* FOV cam to come close to recording anything near the sides of the windshield where the car pillar is located.

Unfortunately, not many Viofo rear cams have a 170* FOV. The A229 has a 160* FOV only but is wider than 140* FOV. What I was thinking is to move the rear cam back a bit from the windshield, so the FOV will appear to be wider. It may not work as intended with a 140* FOV but a 160* will work better for this fix. Place a piece of plastic with depth to it on the rear windshield. Then stick the A129 Duo rear cam and windshield holder to the piece of protruding plastic.

This sets the rear cam back from the rear windshield giving me a wider FOV of the windsheild area. This way if someone were to stand near the side of the windshield where the car pillar is, it will be recorded. What is everyones opinion about this work-around? And what other rear cams have 170* or greater FOV (any 180* FOV rear cams out there, I know it gets distorted into a fish-eye scenario)?
 

TonyM

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The rear windshield is a good, solid mounting platform for a camera. I would be concerned about vibration on your protruding plastic section.

Moving the camera further inside the vehicle may adversely affect the metering by recording less road and more of the things around it, including the trunk of your car. At the extreme case, take a look at how interior cameras (A139, T130 etc.) record what happens outside - often the exterior is over-exposed. Moving the camera just a few inches may be fine though.

If you really want to go for wider coverage, you can remove the current lens and replace it with a wide-angle lens. For a while I used a 170deg lens in a side-facing A129 (front camera). I had to cut away part of the lens housing to fit the wider lens and avoid vignetting, but it worked really well. Note that if you increase the angle of view and keep the same resolution, you will have an apparent loss of detail because those 2MP will be spread over a wider area, so it will become harder to read number plates or any other details behind you.

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Thanks for the tip. I will need to play around with the rear cam placement. I may get the A229 which has a 160* FOV for the rear cam. Wish it was 170* but it is what it is.

Where did you get the wider angle lens? From one of the 170* FOV Viofo rear cams?
 

kamkar

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10 years, many dashcams
you can buy lenses with just about any property in a range of online stores, Aliexpress aso

The lenses our dashcams use are called S mount or just 12 mm ( fine thread )
The things to look at is if the lens support the size of the sensor in the camera, also the lens must have a IR cut filter ( not normal for CCTV use as then most often the IR cut filter are in the base the lens screw into )
Most sellers will install a IR cut filter if your lens of choice do not have it, but as lens swapping have become popular in action cameras ASO many also have a selection of lenses where the filter are already there

Regarding FOV you also have to be careful, is it the diagonal angle listed or the horizontal one ? a lens that might say 170 it could be the diagonal angle and so horizontal it might only be 130 degrees.

Needless it have to be a quality lens too, the one above you can also just make out it is a 5 megapixel lens ( which you will need for a 1440p system, for 1080p a 2 megapixel will be enough, and on the other end you will need at least 8 megapixel lens for a 4K camera.
Lenses come in all kind of qualities, some useless garbage with plastic lens elements, other extremely expensive.
Also you of course need to look at the "F" value of the lens, the smaller the number the more light it let thru, and in dashcams you want as much light as possible, not least at night.

 

TonyM

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Thanks for the tip. I will need to play around with the rear cam placement. I may get the A229 which has a 160* FOV for the rear cam. Wish it was 170* but it is what it is.

Where did you get the wider angle lens? From one of the 170* FOV Viofo rear cams?
Don't get too hung up on the FOV numbers quoted by camera manufacturers and lens resellers. They are not accurate.

This is the lens I bought. It's apparently 185 degree horizontal field (on a 1/2.5" sensor)
 
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Thanks to both Kamkar and Tony M for sharing the info above. I am interested in the horizontal FOV.

Maybe I am not understanding dashcam lenses. Why does the lens have a plastic screw on the end? Is the lens seperate from the sensor? I ask because if the lens as pictured has a screw at the end, how does the lens connect to the sensor of the rear dashcam?

I assume the A129 Duo has a 1/2.5 sensor? I will check out the link. If I don't want to lose any detail in the recorded video is the one you linked to the best quality or is there a better one?
 
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kamkar

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Some times a lens are fixed with a little " nut" on the thread you back up tight against the mount " socket" to lock the lens in place, other times a grub screw in the female thread in the mount secure the lens by getting screwed in untill it bottom out against the thread on the lens.
BUT in most cases the lens are just secured with a little glue, and this can some times be a pain to get off. ( if doing the same you want to use a mild glue, do not use CA glue as it is very permanent and fumes from it might ruin lens coating )
I have at times used lacquer or just paint to act like a glue / filler so the lens can not rattle loose.

These are fixed focus lenses, so to focus them you just screw them in until you are in the sweet spot for focus, this demand a live feed from the camera ( AV out to a screen, HDMI out even better as it is HD feed,but HDMI aout are rare on dashcams, and then wifi live view )
And very last and quite trial and error, small adjustments, followed by preview of the recorded footage, so if you have no set off point marked or you have a whole new / different lens this last way can be quite time consuming as it just take 1 degree of turn on the lens to be in focus or off focus.

There are many videos on youtube about how to put a new lens in action cameras ASO , it is pretty much the same just another format of camera, but lens ASO are the same kind.
 
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