4K vs 1080p Telephoto

[TonyM]

For some time I have supported the idea of using 2No front-facing 1080p cameras - one with a standard wide angle lens, and another with a telephoto lens to pick out details than cannot be resolved by the standard camera.

This concept has been discussed at length in other threads, including:
Mobius Varifocal Zoom IR
Mobius 5MP Varifocal Zoom 6-22mm ƒ/1.6
Mobius Telephoto Dashcam

Since we are starting to see good quality 4K cameras become available, I wondered whether a single 4K camera could achieve similar results to a dual 1080p wide-angle and telephoto setup.

My test cameras:
1080p wide-angle : Viofo A129 at 1080p30
1080p telephoto : Mobius Maxi at 1080p30 with a 6-12mm varifocal lens set to the widest FOV (approx 6mm)
4K wide-angle : GitUp F1 at 4K30 with a Viofo A129 lens (FOV slightly wider than standard A129)
NOTE: I'm not going to comment on image quality since these three cameras are very different. I'm mostly concerned with the FOV and the amount of detail that can be captured, or lost.

Static Scene
1080p Wide Angle

4K Wide Angle

1080p 6mm

As expected, the 4K image offers more detail across the whole frame than the 1080p wide angle image. The telephoto resolves more detail in the centre of the view than either wide angle camera. We can even read the number plate YC11 JKV on a car approx 25-30m away.

To get an idea of how much detail the 4K image contains, let's look at a direct 1920x1080 crop from the middle:

There's not as much detail dead-ahead compared to the telephoto camera - we can't make out the same YC11JKV plate - but there is substantially more detail than the standard 1080p wide angle image. Even at the edges of the frame we can read number plates that are completely lost on the 1080p view, and of course outside the FOV of the telephoto lens:



SUMMARY:
- 1080p wide angle and telephoto combination gives average resolution across the typical dashcam view, with excellent resolution in the centre of the view
- 4K wide angle gives very good resolution across the typical dashcam view, but less resolution than a dedicated telephoto camera in the centre of the view

 

[TonyM]

Driving Comparison - Junction
Driving through a junction, the wide-angle 1080p camera gives a good overall view of cars ahead and in adjacent lanes, the colour of traffic lights etc. The telephoto dashcam can pick out number plates from a greater distance when driving at speed, and can give us an idea of what the driver in front is doing when we're close up near the stop line. However the telephoto dashcam misses a lot of what is going on around the car, especially when the traffic route is not straight.

Taking a look at the 4K camera, and combining its original wide angle view with a 1080p crop from the centre of the FOV, we get a similar effect to that seen above from using 2No cameras:

As before, the 4K video records considerably more detail than the 1080p camera, and does so across the entire frame rather than just in the centre of the view, as seen in this 100% crop:



Comparing the 1080p 6mm video directly to the 1080 crop from the 4K camera, the telephoto camera resolves a little bit more detail as expected, at the expense of being limited to a narrower FOV.

 

[TonyM]

Driving - Country Road

This video demonstrates how a telephoto camera is useful for recording what is happening straight ahead, but crucially misses the vehicle coming the other way on the bend, with only a wing mirror visible.

The 1080p wide angle camera barely captured the number plate :

The 4K wide angle camera with higher resolution does better, partly because it resolved the number plate at a greater distance whilst the other car was travelling more towards than across the field of view.

Looking at the second car that passed by, this time the 6mm telephoto camera gets a much better view.

A 1080p crop from the 4K video delivers a nice sharp capture

The standard 1080p wide angle camera is OK, but only just captured the important details.

 

[Harsh]

4K + narrower lens, should balance things out.

 

[TonyM]

Conclusions

1080p Wide Angle & Telephoto

• Average detail across the wide angle view
• Excellent detail in a narrow central field of view
• Easy to supplement an existing dashcam with a telephoto camera
• Can use high performance IMX291 in both cameras at reasonable cost
• Redundancy by recording on two devices increases data security

Single 4K Camera

• Good detail across the wide angle view, with better-than-1080p detail at the edges
• Only one camera on the windscreen
• Only one power supply & microSD card
• No 4K Starvis option available yet

I am frequently surprised by how much more detail is recorded in a 4K video than 1080p. The ability to pick out potentially important things such as car number plates, or whether other drivers are using their phone whilst driving, can be crucial in the event of an accident.

In recent years I have used a 1080p telephoto camera alongside a normal dashcam, to give more reach and record that extra detail in the centre of the scene. Currently I do this for both front and rear facing cameras.

Now that good quality 4K dashcams are becoming available I can see some advantages to using just one high performance camera.

 

[Nigel]

The advantage of the telephoto is that you are not limited to the 2x zoom of the 4K (vs 1080), you can have 4x or 8x.

However, even at 2x zoom, quite often the number plate you are trying to read is off the edge of the image, in fact if you are going around a sharp corner then most of the other lane can be off the side of the image and thus plates there never come into full view. With the 4K, that is not an issue, you have 2x zoom across the full field of view, so I think for general dashcam use the 4K is going to be the winner, and a professionally made twin lens (wide and telephoto) dashcam isn't going to have more than 2x normal FOV for the telephoto lens. Maybe it can have a wider FOV for the wide lens, a 180 degree + 110 degree lens combination might make a good combination, although then if a plate is off the side of the telephoto, it wont be readable in the 180 degree either due to lack of pixels per plate.

You are using a lens from a 2K camera for your 4K camera, looks a little blurry, with a proper 4K lens the zoomed in image can be just as sharp as a normal 2K lens without the zoom, in fact I'm finding it sharper since the A129 Pro doesn't seem to suffer from the Novatek sharpening that we have seen on almost every dashcam for the last few years and which seems to hide the last bit of detail at pixel level.

This video is 4K at the bottom and 2x zoom (=1080) at the top simulating the 1080 telephoto. on the left hand bend it catches the bad driver who should be in the other lane, on the right hand bend the other vehicle never appears in the telephoto view. The last bit shows the other problem of a telephoto - always looks like you are following too close and misrepresents the speed! Also shows the detail from 4K, if YouTube allows you to read the garage name under the number plate? I can on the original, I zoomed in a bit further at the very end in case you are watching on a phone:

P.S. Don't expect the best of 4K quality, it was uploaded to Youtube at 19.2 Mb/s, and the camera recorded the first bit in 4K at 3.8Mb/s

 

[kamkar]

It is for detail further away i run a zoom camera, but really not super fine detail.
It is more like what are a few indistinguishable pixels on a regular camera, and really not that far away, with the zoom camera you can see it is a person walking and you can see he wear jeans or something jeans colored and a black jacket, and he is carrying a white plastic bag.
And that is a hell of a lot more detail than " i assume its a person walking there" you can take from the footage of a regular dashcam.

I think some times some people are too obsessed with the level of detail, and not least we often see this when the talk fall on night footage.
I feel i demand a lot less of my cameras than many seem to do,,,,,, but i will of course take all the detail and information's i can pull from my footage, and that are also much more than i feel are adequate to secure i don't get blamed for something i should not be blamed for.
So from a personal perspective i am easy to please, so i often have to be pretty anal commenting on the footage of cameras, which are also alright as we should all strive to do better in all aspects of life.



I wonder why i sound so sanctimonious today.

 

[Nigel]

I think some times some people are too obsessed with the level of detail, and not least we often see this when the talk fall on night footage.

For an accident camera, most of the time we only need to see what happened, and that does not need much detail, 720 is OK. But sometimes we need identification. Reading plates can be sorted by a good 4K camera, or by a telephoto lens if the plate doesn't fall off the side of the image, but sometimes you also need faces. Looking at Tony's images above, the only good image of a face is the guy with the shopping trolley! Although the police officer is also probably identifiable in the telephoto image, but probably only because the windscreen was in shadow at that point.

Trying to get the face of the driver of the black truck that cut the corner on my video, it is not easy when people are hiding behind darkened glass, even with a 4K camera:


No problem with the resolution, but I think the next step after 4K needs to be more bit depth, 8 bit video is not sufficient, we want 10 bit video for the next generation of dashcams...

Having said that, I do have the number plate, so I don't think the police would have any difficulty deciding if that was the vehicle owner or not, so there is not much chance of escape. Probably not a good idea to lie about who was driving any more, the consequences can be severe!

 

[TonyM]

quite often the number plate you are trying to read is off the edge of the image, in fact if you are going around a sharp corner then most of the other lane can be off the side of the image and thus plates there never come into full view. With the 4K, that is not an issue, you have 2x zoom across the full field of view, so I think for general dashcam use the 4K is going to be the winner

I agree.

 

[SawMaster]

Not so much "apples and oranges" but more like "lemons and limes". The telephoto excels at a distance with the 4K being equal but spread over a wider area which is probably more useful in a single dahscam But we can have both so no need to drop either approach, and now we open the possibility of a 4K with telephoto which should be able to show errant nose hairs at 500M distance

Phil

 

[Nigel]

...and now we open the possibility of a 4K with telephoto which should be able to show errant nose hairs at 500M distance

Phil

I think you might need 8K for that, but we are going to have a problem with the limitation of the optical resolution of our laminated windshields before we get that far!

 

[jokiin]

I think you might need 8K for that, but we are going to have a problem with the limitation of the optical resolution of our laminated windshields before we get that far!

Speaking of which a friend came for lunch today that had just purchased a brand new Honda Odyssey, noticed when they were leaving and looking across the street at an angle through the front windshield that the distortion was clearly visible, very noticeable

 

[Nigel]

Speaking of which a friend came for lunch today that had just purchased a brand new Honda Odyssey, noticed when they were leaving and looking across the street at an angle through the front windshield that the distortion was clearly visible, very noticeable

There seems to have been a trend for that over the last few years, suspect it is mainly to reduce noise, the glass won't resonate as much if it varies in thickness. Might be to reduce weight by removing glass thickness in the centre where it doesn't need to be as strong.

Not sure it's an optical problem, just provides a distorted view, although it might put the colour balance/exposure out at the edges where light coming in at the edges of the image has had to pass through a lot of glass.

 

[jokiin]

There seems to have been a trend for that over the last few years, suspect it is mainly to reduce noise, the glass won't resonate as much if it varies in thickness. Might be to reduce weight by removing glass thickness in the centre where it doesn't need to be as strong.

it looked like a cheap aftermarket windscreen even though it was the OEM one, car was only a few days old, smacked of poor quality actually

 

[TonyM]

One big factor that counts against current 4K cameras is that they cannot compete with the likes of a Sony Starvis 2MP sensor for low-light sensitivity. The new A119 V3 with a 5MP IMX335 Starvis sensor is close to bridging the gap, and provides a reasonable balance between resolution and sensitivity.

I have considered using a 4K wide angle camera and a 1080p Starvis camera. Now, do I leave the 1080p Starvis as wide-angle, or put a telephoto lens on it?

 

[Dashmellow]

it looked like a cheap aftermarket windscreen even though it was the OEM one, car was only a few days old, smacked of poor quality actually

You might recall my saga that began exactly a year ago when I had a replacement windshield installed that was so warped at the corners that the wipers would lose contact with the glass. The manufacturer's distributor claimed at the time that it was "in spec" and refused to do anything about it. The glass shop showed a lot of integrity however and they replaced it three times. Then when the third one exhibited the same problems (slightly better than the previous two but still not good) they replaced it a fourth time at their own expense with a genuine OEM windshield from Toyota that is flawless. The aftermarket for replacement windshields appears to be flooded with inferior quality goods from China these days.

My photographs shot in my driveway clearly showed the warped glass which was difficult to see at the glass shop without the canopy of trees overhead.

These cheap windshields had a second issue that I was unable to document. At night, with car headlights coming through the glass from vehicles in the oncoming lane there would be a subtle but noticeable distortion like a diffused speckle pattern that was rather distracting. On longer night time trips it would cause eye fatigue and was very annoying. At first it was difficult to tell if this was a legitimate problem or not because it was very reminiscent of the badly pockmarked windshield I had just replaced but the OEM Toyota glass I finally ended up with is optically clear.

So, yes the quality of glass in one's windshield does indeed affect the image quality of dash cam videos.

 

[TonyM]

The distortion is really obvious when you see reflections like that! You don't see that on new cars in the showroom.

 

[Dashmellow]

The distortion is really obvious when you see reflections like that! You don't see that on new cars in the showroom.

And you don't see it on any other cars out on the highway either as I intially tried to explain to the glass shop. When this first happened I spent a lot of time checking out other cars to see if I could find another that had a windscreen like mine but never did. Without the photos I would not have been able to get the glass replaced each time. Of course, there was the business of the wiper blades losing contact with the glass at the corners too but I was able to demonstrate that down at the glass shop.

 

[jokiin]

You might recall my saga that began exactly a year ago when I had a replacement windshield installed that was so warped at the corners that the wipers would lose contact with the glass.

actually it was the first thing that came to mind when I noticed it, I'm used to seeing poor quality aftermarket glass, was surprised to see how bad a brand new OEM one was though

The aftermarket for replacement windshields appears to be flooded with inferior quality goods from China these days.

indeed

So, yes the quality of glass in one's windshield does indeed affect the image quality of dash cam videos.

I don't see how it could not affect it in some cases, some of them are very poor quality

 

[Dashmellow]

actually it was the first thing that came to mind when I noticed it, I'm used to seeing poor quality aftermarket glass, was surprised to see how bad a brand new OEM one was though

indeed

I don't see how it could not affect it in some cases, some of them are very poor quality

Several years ago I replaced the sliding glass door that opens onto my deck. The old doors had glass that was perfectly flat and clear, so much so that at night you could see yourself perfectly in it like a black mirror. I recall my ex-wife used to check her outfit in the "black mirror" just before we'd step out for a night on the town. The new door, which was rather expensive and of high quality has glass that is noticeably distorted, so much so that you can't really even see yourself in it. It's just the way things are these days.