Field of view angle

[Cedar1]

First - Greetings. This is my first post to this forum. I hope you are all doing fine, driving safely and enjoying life.

My question is about what you considered acceptable/required FOV angle.
Some dash cams labeled at 120, some 170, etc.
Interestingly enough, looking at this thread:
https://dashcamtalk.com/forum/threads/night-2-b40-a118-vs-panorama-vs-mobius-b-vs-mini-0803.6312/
The Panorama seems to have the widest angle, though it's published as 150 degrees while the b40 as 170.

I actually considered getting 2 mobius cameras, side-by-side, so to cover a greater area.

Thoughts?

 

[jokiin]

the Panorama has 154 degree diagonal view, the 170 quoted on the B40 is a max spec of the lens, not the actual achieved results, the viewing angle is less that that of the Panorama

 

[2000rpm]

Wider field of view puts exponentially greater demands on the lenses and sensor. Putting 120 degrees onto a 2.1MP sensor will show much more detail and a much more 'zoomed-in' image than putting 170 degrees onto the same sensor.

 

[jokiin]

it's not about how demanding something is, the wider view lenses have a much smaller focal sweet spot and things appear further away than they really are, yes you can capture more peripheral detail but if less of it is in focus at any given time is that worth the trade off?

 

[Sparkydave]

Welcome to the forum

SD.

 

[2000rpm]

it's not about how demanding something is, the wider view lenses have a much smaller focal sweet spot and things appear further away than they really are....

OK, let me re-phrase what I said.....

A camera with a 120 degree field of view and a 720p image (1MP sensor) will show about the same level of detail as a camera with a 140 degree field of view and 1080p image (2MP sensor).

 

[jokiin]

sorry, don't agree with that

 

[JooVuu]

OK, let me re-phrase what I said.....

A camera with a 120 degree field of view and a 720p image (1MP sensor) will show about the same level of detail as a camera with a 140 degree field of view and 1080p image (2MP sensor).

Hi @2000rpm
That unfortunately is not an accurate statement in any shape or form and is factually incorrect.

If you want to do this as a 'just looking' test, then yes, they may look similar(ish), however, if you are driving along and are caught in an accident, detail is everything, and pausing a frame and being able to blow things up - then that is where your statement looses all credibility. There's more to the video than just what you briefly see.

Kind regards,

JooVuu

 

[2000rpm]

Hi @2000rpm
There's more to the video than just what you briefly see.

A larger field of view requires a larger sensor if the resolution is to be retained. If the sensor is trying to 'see' a wider view, it can't devote as much of its area to each detail as a cam that's focusing on a smaller field of view.

If we have a 720p width sensor and a 1080p width sensor (1MP and 2MP), at a given distance, each pixel would represent an object of the same size if the field of view of the 720p cam was two-thirds the width of that of the 1080p.

If a 1080p sensor 'sees' a 30ft wide field of view, that's 36 pixels assigned per foot of image width.
If the field of view is narrowed to 20ft, that's 54 pixels per foot.
If the field of view is widened to 40ft, that's 27 pixels per foot.

Going from 120 degrees to 140 degrees increases the width of the image by about 50%. Going from 120 degrees to 150 degrees roughly doubles the width of the image. So you can imagine the examples above being 120 degree, 140 degree and 150 degree cams using the same 1080p 2MP sensor.

 

[Deleted member 46308]

Welcome Cedar1

 

[kamkar]

I would prefer a front and rear camera with a narrow FOV over a single front camera with a huge FOV.

I am not too bothered with what sneak in from the side or capturing that, my narrow FOV camera will dokument i was not doing anything wrong, so if anything happen it must be the fault of the other guy in the margin.

Overall i do prefer 360 degree coverage with 4 cameras, not cuz i want to capture some one actually hitting me, but side cameras allow for me capturing a lot of cellphone junkies, and i like to expose those on youtube, though that might break some Danish laws, but my footage remain up untill a judge order me to take it down.

I think my current front camera have a 150 Deg ( actual ) FOV and thats plenty for me, if need be i would be willing to trade off 10 - 20 deg FOV .

 

[Cedar1]

Thanks guys.
My ask was more about what you consider ascsuitable coverage than the technical/cost challenges of the optics and sensor.
From a technical standpoint, if money is not a concern, i am pretty sure you can have lens design that will out-resolve a sensor, for most focal lengths, fisheye or corrected. But such optics cost money.

Kamkar1 mentioned an interesting point: dobi care is someone sneaks up to me from the sides?
Well, a driver is expected to check his peripherials, and many times you have those darn scooters appearing out of nowhere or your blind spot. Having a 360 view of an incident can actually make or break one's case.

This is why I was thinking of getting 2 cameras to effectively cover the front 180 degrees.

 

[efcm]

If you take one camera 90º and one 170º viewing angle, place it on your car side by side, and you have a car 10 meters in front of you, when you see the film made by the 90º the car in front of you is 10 meters away, when you check the film of the 170º the car "is 20 meters" in front of you.

Imagine someone cuts you off in the road and you rear ended him on the 170º it looks is very far from you, and people will say that you where distracted because you have plenty of time to brake and avoid collision.

I really don't care a lot of what is going on on my side, i prefer a realistic view of what happen in my front to prove that i was driving right.

Your eye have a good view on a 60º the rest of the human eye is periferic vision.

 

[Cedar1]

If you take one camera 90º and one 170º viewing angle, place it on your car side by side, and you have a car 10 meters in front of you, when you see the film made by the 90º the car in front of you is 10 meters away, when you check the film of the 170º the car "is 20 meters" in front of you.

Imagine someone cuts you off in the road and you rear ended him on the 170º it looks is very far from you, and people will say that you where distracted because you have plenty of time to brake and avoid collision.

I really don't care a lot of what is going on on my side, i prefer a realistic view of what happen in my front to prove that i was driving right.

Your eye have a good view on a 60º the rest of the human eye is periferic vision.

You are talking about the perspective differences between different focal lengths. A meter is still a meter, it does not matter if it recorded on a telephoto or superwide angle lens.
In other words, if you are worried about false impression due to perspective, you can always take a reference photo, say of lines on the ground 1 meter apart, or any other marker. With that you can show exactly how far objects are from each other in a photo.

 

[efcm]

Cedar people believe on what the see.

The main purpose of a DVR is to show beyond any doubt what happened, if you need to take more pictures to explain that what they are seeing its "not real" the DVR you have its not the best to get the job done.

 

[Cedar1]

Its not about believes - it is about facts.
Facts can support or dismiss an optical illusion, which would "upgrade" believing into knowing.

A judge, an insurance adjuster, a police officer - they want facts, not impressions.

A dvr is there to show that in case of an incident i was not at fault. A wider FOV can only produce more evidence to support that - not less.

 

[SawMaster]

I won't join the argument, but if your cam shows that you were not at fault then it has done it's job. It matters little if you can count the hairs on someone's head in the car that ran into you or not. They don't even have to be visible on your cam. If someone beside you out of the FOV hits you, any dashcam will show enough to prove that you were completely in your lane doing nothing wrong when it happened; that is all you really need to prove.
If your budget is large enough you can have the best the world can offer you but anything beyond proof that you did no wrong is not going to make much difference in a courtroom because at that point your case has been won, the Judge's gavel will be dropped, and anything more simply goes back home with you to be put on YouTube where their video compression will lose all the details anyway.

Phil

 

[2000rpm]

.......If someone beside you out of the FOV hits you, any dashcam will show enough to prove that you were completely in your lane doing nothing wrong when it happened; that is all you really need to prove. .......

There have been 'cash for crash' instances in the UK where someone gestures to let you come out of a T-junction, then once you begin moving they accelerate into you, claiming you did not give way to them. Only a side-mounted cam can show the criminal's gesture allowing you to exit, followed by their acceleration into the rear-side of your car. Not many people have side-cams.

I've attached a screenshot capture from a basic 720p cam (not the best light conditions but it's the only decent screenshot I can find due to using a small memory card) which shows the area where such criminals will be when they gesture someone to exit a junction before ramming them. Bear in mind in the UK we drive on the 'wrong' side of the road so the second attached picture is a flipped image which is how many people will see it in their country.

 

[2000rpm]

....A dvr is there to show that in case of an incident i was not at fault. A wider FOV can only produce more evidence to support that - not less....

I had an 'incident' a few months back where it was dark and I was following a lorry along a 60mph road. Suddenly the load starts falling off the lorry and into my path.
Despite me hitting several pieces of wood and cardboard and flashing my headlights, the lorry didn't stop.
I had to stop because debris was wedged under my car so I was unable to chase him.
Fortunately no damage was done and it simply wasn't worth reporting him because if no damage is caused nobody cares, but in that instance, if I had needed to capture his number plate, experience tells me that I would definitely have benefitted from a smaller field of view camera due to the 'zoom effect' because I find that at safe stopping distances on 60mph roads number plates are not easily read and a wider field of view would have made his number plate even smaller and lower-resolution.

 

[dash riposki]

Here's a crude example of the difference in field of view, an old Mobius, I think 130 degree, vs the A118c, at a claimed 170 degree.
(the first segment is the mobius, second an a118c)

Both cameras are mounted at about the same height on the truck windshield, but about ten inches apart.

For general accident documentation stuff, I prefer the video from the A118C. (Not for posting online) You see a bit more of what is happening to the sides.

I go to the mobius video with the hope of pulling out more detail of things that happened right in front of me. (License plate numbers, etc)

For most accident situations, whether you get the video that proves the other driver was on the cellphone or picking his nose as he ran the redlight before hitting you isn't important if it goes to court. Proving he ran the redlight is all that matters.