Field of View

[2000rpm]

For some time I have been questioning whether many cams give the field of view claimed, or whether different manufacturers are confusing different terminology such as some reporting diagonal angle while others report horizontal angle and still others say one thing but probably mean the other.
So along with a bit of help from others I know with dash cams, and from examining comparison footage posted by reputable others, I approximated the relative field of view of about ten common or readily-available-in-the-UK cams.

The following table gives an idea of the relative field of view (rFOV) of the various cams looked at so far, rounded to the nearest 0.5 to keep things relatively simple. At the bottom of this post are two screenshots - one from a Cobra 840E (rFOV=5) and one from a Panorama (rFOV=10) and you'll see that the Cobra's field of view only sees around half as much as the Panorama, justifying the rFOV of 5 vs 10.

Cam..............................rFOV......claimed
Panorama.......................10.......135h/154d
A118/B40.......................9.5.........170
Blacksys CF-100.............9...........130d
SG9665GC......................9...........135d
Transcend DP200..........9............160
Transcend DP100...........8...........130
LS430W/ NB402G.........8...........140
Mio 528 / Mio538.........7.5..........130
Nextbase 101.................5.5...........120
Cobra 840E....................5.............118
Cobra 840E (720p60)...6.5..........118

h = horizontal angle, d = diagonal angle

And the conclusions?

My results - which admittedly could have errors and I am happy to re-evaluate if queried - suggest that some cams have fields of view that are wider or narrower than we're led to believe.

Even trying to explain away anomalies by noting that some manufacturers report horizontal angles while others report diagonal angles doesn't explain some of the anomalies.

So don't judge the field of view by the claimed angle because it doesn't always correlate with the actual field of view!

Some examples:

The claimed 170-degrees of the A118/B40 gave a narrower field of view than the claimed 154-degrees of the Panorama.

The claimed 160-degrees of the DP200 gave a narrower field of view than the claimed 154-degrees of the Panorama. In fact, the DP200 field of view was only slightly wider than the DP100, and looked closer to only a 10-degree difference despite the claimed 30-degree difference.

Interestingly, @jokiin's 9665 with a claimed 135-degree diagonal only had a slightly narrower field of view than the 170-degrees claimed for the A118C/B40, and was slightly wider than the mainstream cams claiming 130-140 degrees (Mio 5xx, DP100, LS430W, NB402G). It was, however, very similar to the Blacksys CF-100 which claims a similar angle.

The Cobra 840's field of view changes with resolution - oddly it is wider when on 720p than on 1080p (something I've commented on in the past) so clearly while it might give 118 degrees, it can't be giving the same angle on both resolutions.

Please note this topic isn't intended to be 100% accurate, but it is intended to get people thinking about - and questioning - their camera's or proposed purchase's claimed field of view.



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[jokiin]

SG9665GC......................9...........135d

SG9665GC is 135° Diagonal and 112° Horizontal, those are actual figures, we don't get into marketing fluff trying to make things look better on paper or whatever, everything we quote are real numbers

Horizontal figures that most quote are the spec of the lens but not the actual numbers achieved with the sensor they use which can sometimes be about 30° less than the total the lens can offer, different sensors can yield different results even when used with the same lens, our lens is a 156° Diagonal but it depends which sensor it's used with as to what field of view it delivers, it varies from 145° to 133° Diagonal, the Horizontal figures vary from max of 122° down to 111°

if anyone else used the same lens I'd bet they'd advertise it as a 156° lens because the biggest number listed, bigger numbers must be better yeah

 

[2000rpm]

Hi @jokiin - please don't think I was in any way criticising your product; I tagged you because I had mentioned your product (which I think is a very good product).

I can see where you're coming from; your sensor is using virtually every pixel so barely a pixel is wasted whereas some other sensors are not using all the pixels and by not using all the pixels the image could be narrower.

But I thought I would raise this discussion because I haven't seen it mentioned on DCT and I think it's worthy of highlighting that we don't always get the angle that the manufacturer claims.

Some people choose cams for 'wide angle' and some choose for 'narrow angle' and some might choose (say) a Transcend DP200 because it claims 160 degrees fov instead of (say) a Blacksys CF-100 because it claims 130 degrees fov, when, in fact, there is negligible difference in the field of view.
Almost certainly - as you suggest - because the DP200 is using a 2304*1296p sensor which may well have 160-degree diagonal view, but that is being cropped down to 1920*1080p and explains why the actual field of view seems more like 130-140 degrees. The CF-100 is using a 1920*1080p sensor with no cropping (as is the 9665 and other cams from SG). Pixel size will also be different; the DP200's higher resolution sensor having smaller pixels - 2.2microns vs 2.8 microns.

 

[jokiin]

Hi @jokiin - please don't think I was in any way criticising your product;

not at all, apologies if you thought that, was just offering some detail to try and help explain why things don't meet advertised specs, we don't lie about our numbers but you can see by the example I gave how confusing it could be and why the numbers don't tell the whole story

 

[2000rpm]

not at all, apologies if you thought that, was just offering some detail to try and help explain why things don't meet advertised specs, we don't lie about our numbers but you can see by the example I gave how confusing it could be and why the numbers don't tell the whole story

No, I didn't think we were heading for bad feelings, but on the internet where we can't see facial expressions or hear tone of voice it's easy for misunderstandings to happen.

 

[Module 79L]

Well, I didn't need to get so "deep" into the deceitful FOV numbers most manufacturers or sellers advertise, it just took me a G1W and a G1W-H to realize that: the first one was advertised as having a 120º FOV, the second one a 140º FOV. They have the exact same FOV, which in reality should be less than 100º.
I didn't know anything about the AT11DA, but from the looks of it the lens was very similar to the one's on the SJCAMs. When I look up the specs it was advertised by many sellers has having a 170º FOV, the "usual" for that type of lens. The only place where I saw a different number was on Gearbest, which was a much more realistic 148º. It is wider than the G1W's but still I don't believe it's that much. My estimate is that it's approximately 120º.
I don't have here with me the snapshots I took from the G1W-H and the AT11DA with the car stopped in the same place but I'll post them later, just to had some more "fuel" to this discussion.

 

[Ralph2]

At the bottom of this post are two screenshots - one from a Cobra 840E (rFOV=5) and one from a Panorama (rFOV=10) and you'll see that the Cobra's field of view only sees around half as much as the Panorama, justifying the rFOV of 5 vs 10.

Are both views from the same spot? It "looks" like one is from farther back and thus shows a wider view.

 

[2000rpm]

Are both views from the same spot? It "looks" like one is from farther back and thus shows a wider view.

They are of the same moment in time, as shown by the position of the bicycle as it turns right (give or take a couple of frames and considering the wide cam is slightly left of centre and the narrow is slightly right of centre).
The narrower angle camera is sitting slightly further forward (it can be seen in the bottom right of the wider-angle cam's view) but as shown by the screenshots I provided on the thread in this > link < it doesn't make a huge difference.

Here are a couple of screenshots from the same two cams, and you can see by the traffic light sequence that it's within a few frames of the same moment:


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[Module 79L]

Ok, here are the snapshots. As you can see by the time stamp, they were taken 4 minutes apart. I kept the same suction cup and in the same place (both camera's T-brackets fit each other's mount) so I could capture the same perspective from both cameras. The suction cup is placed as close as possible to the center of the windscreen, on the left side of the RVM.

 

[Ralph2]

Is the field of view angle related at all to the zoom level? Perhaps I do not understand the finer points.. but I imagine looking through the bottom end of a funnel. That would define the fixed angle of view.. but, if I then magnified what I saw, the view would appear closer.. and be cropped off the sides. Maybe I need another cup of coffee and it will make more sense.

 

[2000rpm]

Is the field of view angle related at all to the zoom level?.

I suppose you could think of it in the same way as the cam having a fixed magnification.

The wider field of view cams have less magnification. Too low magnification and you can't see enough detail.

The narrower field of view cams have more magnification. Too high magnification and you can't get the overall picture.

 

[brownj00]

Thanks for this post and the followup comments. I am less concerned with giving a judge/jury the wrong "impression" of distance or speed, and more concerned with capturing the fact that at a 4-way stop the other car was at fault (e.g. didn't stop). This can be hard depending on the intersection and angles. But I think this is a common accident in the real world where a wider angle dash cam can really help.

I first tried a Cobra with claimed 118 angle, I didn't buy it. Way too narrow in reality. I am testing a Rexing V1 which I think has the same lens & sensor as the A118, and it claims 170 degrees. I like the width but I do see the warping effect- watching the video it looks like I am going too fast but things do not appear very far away. For me the perception issue is not a major concern.

I am now looking at the SG9665GC but was concerned about comments of "135 diagonal but only 112 horizontal". Without knowing any better that sounds much narrower than the 170. Some of the videos of SG seem to show good performance for seeing the the car next to you at a stop light, etc. - maybe around what I am seeing with the Rexing now. So I can't be sure how to consider real world performance based on the different numbers. It is perplexing. Almost like women's clothes sizes!

 

[DT MI]

For what it's worth I have both SG9665GC and A118-C cameras. Regardless of the published specifications the field of view is for all practical purposes is the same.

 

[Module 79L]

I am now looking at the SG9665GC but was concerned about comments of "135 diagonal but only 112 horizontal". Without knowing any better that sounds much narrower than the 170. Some of the videos of SG seem to show good performance for seeing the the car next to you at a stop light, etc. - maybe around what I am seeing with the Rexing now. So I can't be sure how to consider real world performance based on the different numbers. It is perplexing. Almost like women's clothes sizes!

Everything you read in almost every single specs chart is the diagonal FoV. Many manufacturers try to "sell" you false specs, not Street Guardian. That's why they also provide the horizontal FoV numbers, so that people can relate better to what they actually see in the footage (your "real world performance"). When you watch a video filmed with a GC you'll know what a 112º FoV looks like.

 

[2000rpm]

SGZC12RC and Panorama (and probably the SGZC12SS/SG derived from the Panorama) have a real-world field of view that's about as wide as can be found in current dashcams; about 30% wider than average.

The CF-100, DP200, SG9665GC, A118 and JooVuu X have a fairly wide view; about 15% wider than average.
The JooVuu is an exception to the 'wider field of view means less detail' due to its 2560p sensor, although the X-cam still has some teething troubles and won't match the IMX322-equipped cams at night but the X's night performance is a match for the good quality AR0330 cams.

Then there are a lot of cams in the average field of view category: DOD LS430W, NB402G, DP100, Mobius, Mio 5-series - most of them being AR0330-equipped.

The Cobra 840 (or its unreliable brother, the 820) field of view is about two-thirds that of the average mainstream cams, or half that of the really wide angle cams. Things can slip past the Cobra's narrow field of view on bends and its night performance is below that of the mainstream cams, but in daylight anything in its limited field of view is much more zoomed-in and easier to pick out details. Peculiarly, the Cobra 840 field of view is wider when set to 720p than 1080p, although even on 720p it's about 20% narrower than the average cams.

 

[Kip]

Interesting thread. When researching for my first dashcam, the stated FOV wasn't that important as I didn't understand all the different figures quoted. As long as the angle was wide enough to see both A-pillars at the edge of the frame, I'd consider that wide enough for myself. Online sample videos by actual owners or independent reviewers are best for checking stuff like this. It would be nice of course if all manufacturers could be like Street Guardian and post real world FOV figures and not just use the biggest possible number from the lens or sensor.

 

[jokiin]

I am now looking at the SG9665GC but was concerned about comments of "135 diagonal but only 112 horizontal". Without knowing any better that sounds much narrower than the 170. Some of the videos of SG seem to show good performance for seeing the the car next to you at a stop light, etc. - maybe around what I am seeing with the Rexing now. So I can't be sure how to consider real world performance based on the different numbers. It is perplexing. Almost like women's clothes sizes!

probably confusing as we publish the real figures, most just publish whatever the overall lens spec is which can vary depending on which sensor it is being used with, most quote the max diagonal figure of the lens only which is always the largest number, if we did the same we would quote 156° Diagonal as that's the max of the lens, it's not realistic though


Edit: fixed the typo, I wrote 165° instead of 156° earlier for max diagonal of our lens

 

[russ331]

... a lot of cams in the average field of view category: Mobius ...

Mobius is currently available with a choice of two lenses, A & C2.

Both have user-selectable narrow & wide modes. Lens A in narrow mode is 75° HFOV. Lens C2 in wide mode is 131° HFOV.

My Mobius B is 116° HFOV in wide mode, which is a little too wide for my preference, though not quite as wide as that of my SGZC12RC