A139 (Pro) Telephoto Remote Camera

[TonyM]

The 6mm lens I tested before is only a little high than a regular lens.
I am checking a lens designed for car manufacture, the FOV(D) is about 83 degrees, and the FOV(H) is 65 degrees, will it be too wide for a telephoto lens?

A diagonal FOV of 83 degrees is approximately equivalent to a 4mm lens, assuming a 1/2.7" sensor like the IMX291. I think this is too wide, and will not really add much benefit over a regular lens. Especially if the 'telephoto' camera has a lower resolution than the main camera. A pair of 1440p IMX335 cameras would be a good choice though.

If you think the FOV is too narrow for a consumer dashcam at 10mm or 12mm, I recommend that you try to find something in the range of 6mm to 8mm. For a 1/2.7" sensor, that means a lens with a diagonal angle of view in the range of 45-58 degrees.

 

[TonyM]

I am looking at short, compact 8mm lenses like this to match the A139 remote cameras:

Witrue Starlight Lens 3MP 8mm Fixed Aperture F1.5 Big Angle For SONY IMX290/291/307/327

 

[Dashmellow]

I am afraid the 10mm and 12mm lens FOV is too small.
Also we need to balance the lens length, too long does not look good.
The 6mm lens I tested before is only a little high than a regular lens.
I am checking a lens designed for car manufacture, the FOV(D) is about 83 degrees, and the FOV(H) is 65 degrees, will it be too wide for a telephoto lens?

Telephoto lenses by their very nature are physically longer than wide angle lenses. The primary issue for those of us who have been experimenting with physically longer lenses has been whether or not they will touch the glass of the windshield, not how they look.

Personally, I like the way these longer lenses look when mounted in a camera and think they look pretty cool. A physically longer lens would stand out among a sea of other nearly identical looking products on the market and it would broadcast that this is a unique, innovative product with an exclusive capability not available elsewhere. Such a product may well appeal to buyers rather than turn them off.

 

[TonyM]

After moving the 8mm lens to another camera (Mobius 1S), I re-installed the 6mm remote camera as a rear-facing telephoto. I have used this lens previously in a Mobius 1 for the same purpose. I am quite happy with 6mm for a rear camera because it can show what the driver behind you is doing, without being so close that it misses too much action to the sides.

The long barrel lens is a problem for mounting on the rear window glass, so this is a temporary mount on the plastic trim until I find and install a suitable short-bodied 6mm lens.

 

[Dashmellow]

Looks good!

Feels like this set-up needs a polarizer though so you can see the occupants of the vehicle behind you. Perhaps the driver is on a cell phone or engaged in some other distraction.

As a fellow DIY telephoto dash cam enthusiast you know that I find a CPL to be a requirement for these installations. Of course, finding and fitting a suitable CPL to small diameter lenses can be a challenge but it makes a huge difference.

 

[TonyM]

Feels like this set-up needs a polarizer though so you can see the occupants of the vehicle behind you. Perhaps the driver is on a cell phone or engaged in some other distraction.

Yes, I agree. Assuming I can find a short enough 6mm lens, I plan to attach a polarising filter to the remote camera housing, similar to what I did here. If the 6mm lens extends beyond the housing I may need to add a simple spacer, such as a VHB pad each side of the lens.

 

[Dashmellow]

Yes, I agree. Assuming I can find a short enough 6mm lens, I plan to attach a polarising filter to the remote camera housing, similar to what I did here. If the 6mm lens extends beyond the housing I may need to add a simple spacer, such as a VHB pad each side of the lens.

I'm considering adding a rear facing telephoto Mobius M1S to my current set-up so I've been thinking about how I will go about installing a CPL. Very likely, I will devise a version of the DIY CPL I created 4 1/2 years ago for the Maxi camera.

 

[pinoyplaya4life]

Just literally Installed. Made it so the lens can be adjusted to adjust focus. So far I’ve adjusted focus on indoor objects. Will do some testing and recording throughout the next couple of weeks and make some adjustments to optimize focus.

Here’s photo with lens installed so you can see how far it sticks out compared to others.

 

[TonyM]

Just literally Installed. Made it so the lens can be adjusted to adjust focus. So far I’ve adjusted focus on indoor objects. Will do some testing and recording throughout the next couple of weeks and make some adjustments to optimize focus.

Here’s photo with lens installed so you can see how far it sticks out compared to others.

I'm curious to know how you have installed it such that you can adjust the focus, apart from the lens simply being loose in the holder.

Were you able to use the original lens holder without any modifications, M12 extenders etc?

 

[pinoyplaya4life]

I'm curious to know how you have installed it such that you can adjust the focus, apart from the lens simply being loose in the holder.

Were you able to use the original lens holder without any modifications, M12 extenders etc?

No modification to the lens holder and used the stock lens holder.

I just threaded the new lens but did not permanently secure it with any adhesive so I can rotate the lens clockwise or counter clockwise to get microfocus adjustments.

It’s pretty secured in place and requires a bit of torque to loosen or tighten the lens to adjust focus. I’m pretty sure it can stay like this without me having to permanently glue it in place. shock and vibration from driving shouldn’t cause the lens to go out of focus given how tight it is to rotate clockwise or counter clockwise.

I am able to get proper thread engagement without any lens adapter or anything.

If I had to redo this again, the only thing I would have done is gotten a new M12 lens mount that is a direct replacement of the stock one. The stock lens was a pain in the ass to remove since it was epoxied/glued in place. Was able to remove the epoxy with a bit of heat from hair dryer but the threads were glued in place inside too. Had to remove the lens mount from the camera PCB so I could disassemble the stock lens and lens mount. Placed the camera PCB assembly inside a zip lock bag to prevent dust from getting in the sensor in the meantime.

 

[TonyM]

Sounds like it all went well. Let's see some footage after you get it installed.

 

[pinoyplaya4life]

Update:
Haven’t had the chance to test the ~8mm lens much since it kept falling off. It was just ever so slightly too tall for my windshield and didn’t have time to reinstall and put a spacer in between.

I did order a different lens (12mm) which I installed. It was much shorter than the 8mm and had the right specs I was looking for. This fit very well with the interior camera.

Couple sample images (screenshots of the video footage from my iPad, so quality may not be as good) comparing the standard main camera view and the interior camera w/ 12mm installed.

 

[pinoyplaya4life]

I personally prefer the 12mm considering how much gap/space I leave when driving behind someone (similar distance to the first photo of the blue car in front on the parking lot).

This gives me the perfect view of the vehicle with the telephoto lens. The 8mm distance was just too short and didn’t have much advantage over the main camera.

Here’s a photo of how the 12mm lens looks like when installed on the interior cam. It doesn’t protrude as much as the 8mm, so it doesn’t interfere with the windshield.

I plan on installing the 8mm on the rear camera. That’s the next step.

 

[TonyM]

Couple sample images (screenshots of the video footage from my iPad, so quality may not be as good) comparing the standard main camera view and the interior camera w/ 12mm installed.

Those 12mm samples look good and show how you can sometimes (not always) get a better exposure on a number plate at night using a telephoto camera.

What is the lens aperture? Can you share a link to the lens?

 

[TonyM]

I personally prefer the 12mm considering how much gap/space I leave when driving behind someone (similar distance to the first photo of the blue car in front on the parking lot).

This gives me the perfect view of the vehicle with the telephoto lens. The 8mm distance was just too short and didn’t have much advantage over the main camera.

That's a good test, to see if you can make out number plates on the car ahead at your normal following distance - the distance depends on the speed of course, but it's still a fair test for urban driving at 30-40mph.

I'm lucky to have relatively large numbers & letters on our UK licence plates, so 8mm works fine for me but I can see why 12mm might be better for you.

Does 12mm give you enough coverage on bendy roads?

 

[pinoyplaya4life]

That's a good test, to see if you can make out number plates on the car ahead at your normal following distance - the distance depends on the speed of course, but it's still a fair test for urban driving at 30-40mph.

I'm lucky to have relatively large numbers & letters on our UK licence plates, so 8mm works fine for me but I can see why 12mm might be better for you.

Does 12mm give you enough coverage on bendy roads?

Here’s a link to the 12mm lens.

https://m.aliexpress.com/item/4000740411186.html?trace=wwwdetail2mobilesitedetail&spider=y

I got the 12mm last night, installed it and took it for a night drive to make some adjustments and get it setup. I should be able to get some normal driving recordings this weekend and will review (and share) some footage.

 

[Julian23]

I should be able to get some normal driving recordings this weekend and will review (and share) some footage.

Please do.
Maybe I will give it a try too if the results are good.

 

[pinoyplaya4life]

@Julian23 @TonyM

Finally had the chance to capture some daytime videos. Overall, results are great. The depth of field might be too narrow given the aperture of f1.8.

Theres a couple parts of the video. Side by side comparison and identical video in 12mm only full screen so you can see the detailed quality.

Watch it at 4k to get it as close to the real quality due to youtube compression.

I had to reposition the 12mm camera after this video since it’s not centered how I want it to be. Havent tested the new position yet but results should be similar.

 

[Julian23]

The video quality looks good.
Comparing it with the 8mm Telephoto Lens from TonyM I am not sure what I prefer.
Both have their advantages.
The 8mm does capture more of the environment while the 12mm is seeing way ahead.

 

[TonyM]

Finally had the chance to capture some daytime videos. Overall, results are great. The depth of field might be too narrow given the aperture of f1.8.

Theres a couple parts of the video. Side by side comparison and identical video in 12mm only full screen so you can see the detailed quality.

Generally it's looking good. You have better focus on the right than the left side. That's OK for traffic going in your direction, but might struggle with oncoming vehicles on the left side. As you have found, it is often difficult to get everything in focus with these fast telephoto lenses.


I can see why you might want 12mm for those small licence plate characters. Personally I find the FOV is too narrow for anything other than straight roads. On this gentle curve the Silverado is cropped out of the telephoto view. However your 12mm camera can see details that my 8mm did not.