A139 (Pro) Telephoto Remote Camera

[Nigel]

I think this side-by-side example shows some of the positive and negative things about a telephoto dashcam, however when used in combination with a primary camera they have the potential to complement each other rather than simply duplicate the same information in both video streams.

Your FHD telephoto appears to have 2x magnification over the 2K A139, so you could have got the same detail from a 5K camera with a standard lens (if it existed), and then you would not have cropped detail at the sides/corners, and if it was Starvis-2 then the extra dynamic range would sort out the highlights/shadow difference.

Would be interesting to compare your telephoto camera with the A139 Pro... shouldn't be much difference in detail, but twice the field of view?

 

[TonyM]

Would be interesting to compare your telephoto camera with the A139 Pro... shouldn't be much difference in detail, but twice the field of view?

I know you're an advocate of high resolution over telephoto. I often wondered the same, comparing a 1080p telephoto to 4K cameras like the A129 Pro, GitUp F1 or the Mobius Maxi 4K.

Whether it's the difference in metering, bitrate (bits per second per pixel), sensor spec or lens quality, I've usually found that I preferred the output directly from the 1080p telephoto camera when compared to a cropped view from the 4K camera. Maybe that because all those 4K cameras use the same sensor?

I will compare this telephoto against my A139 Pro when it arrives, and if I find that the FHD Starvis 1 telephoto offers no advantage over the 4K Starvis 2 wide angle camera then I will stop using it.

 

[DAP]

The separate telephoto lens allows one to do optimizations like running a different exposure on the two cameras, or running without an IR filter on one of them.
I do wish we had some control of the maximum exposure time, or at least prioritize exposure time over ISO setting.
Sometimes I think the limitations on 4K results are limitations on the quality of the lens, and results of the compression algorithm. There seem to be enough pixels, but the plate is still unreadable.

 

[Dashmellow]

I've usually found that I preferred the output directly from the 1080p telephoto camera when compared to a cropped view from the 4K camera.

Especially with the reduced or eliminated motion blur, enhanced plate capture and optimized exposure when compared to the same frame of oncoming vehicles from a typical wide angle camera, regardless of resolution.

 

[viofo]

A couple of days ago I repositioned the 6mm camera. It was high on the driver's side (right) at the very top of the wiper arc, but rather obvious from both inside and outside of the car.

Now it is mounted on the frit on the left side and barely visible from the outside. As you can see, the lens is almost touching the glass. If I want to try a larger 8mm lens I will need to modify the mount with spacers.

View attachment 62355

Moving the camera down a bit now shows the front edge of the car along the bottom of the video, as seen in this comparison with the A139 main camera. Whilst I think this is useful to show context in a telephoto video if viewed on its own, I would rather have a bit more reach from an 8mm lens.

View attachment 62358

View attachment 62359

This example looking towards the sun also demonstrates how the metering on a telephoto camera is less affected by bright areas in the sky (no CPL on either camera, both set to EV+0).

What do you think about this version, it is much shorter than your version.

 

[kamkar]

The long "barrel" is a challenge i think, i dont think you could sell something that look like that.
The 12 mm lens i use in my tele camera are short.

 

[TonyM]

The long "barrel" is a challenge i think, i dont think you could sell something that look like that.

I tend to agree that most consumers will not want a long lens, even for telephoto purposes. After all, they now have telephoto lenses in smart phones, without a big lens sticking out.

 

[TonyM]

What do you think about this version, it is much shorter than your version.

That is about 10mm shorter in physical length than my 6mm lens, so it would work for a larger range of windscreen slope angles and would be less obvious to others. I think a shorter lens is attractive for a consumer product.

The main performance difference is that it is F2.0 aperture, compared to my lens at F1.2. On a positive note the F2.0 lens has less distortion, although I don't really notice any distortion on my telephoto so that might not make much difference.

The Mechanical BFL of 5.89mm should be OK to use in the A139 remote camera without an extender.

 

[TonyM]

A139 Remote Camera - 8mm Focal Length Telephoto

A few weeks ago I ordered an 8mm focal length lens from AliExpress, which arrived at the weekend:
4K Lens 12Megapixel M12 1/1.7" 8mm







The 14mm barrel diameter is 'just' small enough to slide through the existing opening on the A139 rear camera, which was a consideration in my purchase.
Original rear lens still in holder on the left / new 8mm lens within the camera housing on the right.



The MBF of 6.8mm is only 1.7mm more than the 6mm F1.2 lens I have been using so far, but it was just enough difference that the new lens did not engage the threads of the M12 holder. I had measured the depth of the lens holder at 8.8mm before buying the lens which I thought would be enough, however the sensor has a certain thickness which I did not measure and this turned out to be an oversight on my part.



I do have an M12 extender, but that pushed the lens too far away from the sensor. So, the only real solution was to replace the lens holder. Thankfully, I have a few boxes of spare parts

It turns out that the 12mm deep lens holder from a Mobius C2 camera fits exactly! Well, nearly exactly. I did have to make a 1x1mm snip out of the RF shield for the moulding on the side of the lens holder. I was surprised that the PCB fixing screw centres were identical (17.5mm?), as was the 15mm square base which as you can see was crucial to fit within the RF shield.



The good thing about this lens holder is that it has a tiny grub screw to secure the lens, which is just as well because there was not enough space within the housing to fit a threaded lens collar. After some testing to determine the best focus position I will secure the lens with some UV glue.

Thankfully it all fits together neatly without any modification to the camera housing

 

[TonyM]

A139 Remote Cameras - 6mm & 8mm Lenses

I have both 6mm and 8mm remote cameras installed together on the passenger side (left) - the main A139 is on the driver's side (right). And yes, I have the 6m long rear camera coax cable stuffed into the headliner!



Due to the extra length of the 8mm lens, I mounted it using a small 3d-printed wedge to ensure clearance to the glass. A shorter 8mm lens would be preferable for cosmetic reasons, however I can mount this long lens on the frit where the 6mm camera is now, and then it will be hard to see from the outside.

 

[Julian23]

This is looking nice.
Cant wait for the results

 

[kamkar]

If i could choose a tele camera for a 2 / 3 channel system instead of a interior camera, that is what i would do for sure.
Even if i have done it for years, and dont go to that camera often for footage, then i would like to swap out my DIY tele camera with something factory made.

 

[TonyM]

6mm vs 8mm - Field of View Comparison (6mm left / 8mm right)



There is not a big difference in the width of the scene recorded by each camera. The front edge of my car appears along the bottom edge of the 6mm video which could be useful to provide context if used as a standalone video. However my intention is only for the telephoto to complement the main wide angle camera, so I don't think I need that context within the telephoto video. The reflection of my dashboard is less intrusive in the 8mm image, which might be because the 6mm lens is almost touching the glass. That dashboard reflection may also be the reason for less contrast on the 6mm camera.

For reference, this is the wide angle view on the A139. It is interesting that both telephoto cameras have a similar colour profile, including the magenta tint which is not apparent in the wide angle video that has a neutral grey overcast sky. Unfortunately the A139 does not offer the user any options to adjust the white balance or any other IQ parameters apart from the EV. I have the 6mm F1.2 camera set to EV-0.3 because I found that at EV=0 it was over-exposed and used longer exposure times than necessary.



100% Crop Comparison - (6mm left / 8mm right)



The 8mm lens records finer detail, as expected. The 12MP rating and F1.8 aperture also help in this regard, compared to 3MP and F1.2 for the 6mm. I can also see that the 6mm has significant chromatic aberration and less contrast.

I expect the 6mm F1.2 to have less motion blur than the 8mm F1.8, so it will be interesting to compare performance on the road rather than in a car park.

 

[pinoyplaya4life]

What do you think about this version, it is much shorter than your version.

Do you have a link to this shorter version 6mm lens?

 

[TonyM]

A139 Pro 4K HDR and 8mm Telephoto Remote - Into Low Sunlight

I bought an A139 Pro to replace the regular A139. I am using the same 8mm telephoto remote camera.

Although the 4K wide-angle and 1080p telephoto lens capture the scene with a similar pixel density, I have found that the differences in metering and HDR on vs. off result in two quite different video versions. Sometimes one is better than the other, but I like having both.

In this example I could identify 9 out of 13 oncoming vehicle number plates with both cameras, but it is the difference in exposure that stands out.

4K30 46Mbps, HDR-ON, CPL-OFF, EV=0

1080p30 16Mbps, EV-0.3

 

[pinoyplaya4life]

I’m still researching on a compatible lens that requires minimal modification.… specifically a 8mm or 12mm lens that will screw in the existing mount without the need for an extender and already has an IR-cut filter.

Have you stumbled upon any 8mm or 12mm lens that would meet that? I was looking at something with less than 6mm MBF.

The 8mm you used looks like it requires a lens extender. I mean, i could potentially just buy an M12 lens extender and then it would be an easier install than what you did with your 8mm lens.

I would have thought the A139 cameras already has an ir-cut filter built in? Do they not? or is it attached to the lens and would have to be placed onto the new lens? So its best to just get one with it already installed?

 

[TonyM]

I think it will be difficult to find an 8mm lens with a short back focal length.

I recall the 8mm lens that I am using was only just out of focus before engaging the thread into the holder. Trying with an extender it moved the lens too far away to be able to screw it into focus. So for that lens, the only option was a new holder.

All dashcam and action camera lenses I have seen have the IR cut filter attached to the back of the lens.

 

[pinoyplaya4life]

I think it will be difficult to find an 8mm lens with a short back focal length.

I recall the 8mm lens that I am using was only just out of focus before engaging the thread into the holder. Trying with an extender it moved the lens too far away to be able to screw it into focus. So for that lens, the only option was a new holder.

All dashcam and action camera lenses I have seen have the IR cut filter attached to the back of the lens.

Ah gotcha. Yea I figured that the extender would add a bit of distance.

I think I found a 7.8mm 4K lens. I’ll send a link later. I recall the MBF is less than 6mm

Edit: it’s this one. Might be cutting it close.

https://m.aliexpress.us/item/3256802638305097.html?spm=a2g0n.shopcart.0.0.24ff38daHRDS0C&mp=1&gatewayAdapt=gloPc2usaMsite&_randl_shipto=US

 

[Dashmellow]

Ah gotcha. Yea I figured that the extender would add a bit of distance.

I think I found a 7.8mm 4K lens. I’ll send a link later. I recall the MBF is less than 6mm

Please explain why you are concerned with MBF. Do you understand what that term means?

 

[pinoyplaya4life]

Please explain why you are concerned with MBF. Do you understand what that term means?

for the A139 remote camera doesn’t need it to be a specific distance so you can achieve focus since the threads on the mount is limited to how far you can adjust it? Otherwise I wouldn’t be able to mount the lens correctly or it wouldn’t mount at all. I’d have to add a lens extender and to get the correct distance from the sensor to the focal point of the lens.

The lens extender often times would add extra length and not allow you to thread the lens all the way to where it needs to be to get proper focus.