Mobius Telephoto Dashcam

TonyM

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After reading a number of DCT threads recently (@Dashmellow , @dirkzelf , @kamkar1 ) on trying new lenses with the Mobius camera, I decided to have a go myself. My primary aim is to find good fast telephoto lenses which allow the Mobius to operate as a second camera alongside a traditional wide FOV dashcam. For me the function of this second camera is to pick out details that are often too far away to be resolved by a 130 degree (or more) FOV lens. Since vibration and motion blur are more apparent at longer focal lengths, and I'm looking primarily for detail here, the emphasis is on fast lenses which help to maintain a short exposure time.

The first two lenses on test are:
4mm F1.2
https://www.aliexpress.com/item/Starlight-Lens-3MP-HD-4mm-CCTV-Lens-For-HD-IP-Cameras-M12-F1-2-Aperture-1/32667902637.html
upload_2017-11-8_1-47-28.png

6mm F1.2
https://www.aliexpress.com/item/F1-2-Starlight-CCTV-Lens-HD-3-0Megapixel-6mm-M12-Lens-For-HD-CCTV-IP-Cameras/32827674380.html
upload_2017-11-8_1-48-36.png

These two lenses are installed in Mobius 1 cameras side-by-side as seen here, alongside the reference wide-angle FOV dashcam which is my A119.
upload_2017-11-8_1-53-25.png

upload_2017-11-8_1-55-28.png
 
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TonyM

TonyM

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These images are full frames from the two Mobius F1.2 lenses and the A119, recorded yesterday morning. The A119 is recording in 1440p30, whilst the two Mobius cameras are at 1080p30. They all have WDR enabled. Default image adjustment parameters used on all cameras. No CPL filters. Lens profile 'C' on both Mobius cameras. I think the 4mm lens is focused a little bit too close.

1) Approach to junction - 42mph
A119

Mobius 4mm F1.2

Mobius 6mm F1.2


2) Passing junction shaded by trees - 56mph
A119

Mobius 4mm F1.2

Mobius 6mm F1.2


3) Passing parked vehicles - 42mph
A119

Mobius 4mm F1.2

Mobius 6mm F1.2


The higher 1440p resolution of the A119 helps to retain some detail compared to the 1080p Mobius. However the faster F1.2 lenses permit a shorter exposure, reducing the amount of detail lost to motion blur.
 
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TonyM

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Night time testing of the F1.2 Mobius lenses. This time with an individual frame and a compilation video.

Note that it was raining, so there is more glare than normal due to the wet windscreen.

A reminder of the settings:
Mobius 1 @ 1080p30, WDR on, 4mm F1.2 lens
Mobius 1 @ 1080p30, WDR on, 6mm F1.2 lens
A119v2 @ 1440p30, WDR on

A119

4mm F1.2

6mm F1.2


2min compilation video of all three cameras, followed by 2min full-frame of the 4mm then 6mm lenses

So far I prefer the 6mm to the 4mm lens for its extra reach as a second camera. With a sturdy mount there's less camera shake than I was expecting. These F1.2 lenses definitely give a much brighter night video than any of the standard lenses.
 

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The focus seems like it might be "slightly" off on a few of the 4mm and 6mm screen shots. I noticed a similar phenomenon with my 2.8-12mm varifocal lens at times. When that lens was set for the longest telephoto performance (10-12mm) I learned that if I set the primary focus point some 50 or more feet away I could optimize the focus from about 10 feet from my front bumper all that way out to cars in the distance. I found focusing a telephoto M12 lens (at least my varifocal, at any rate) to be different than my typical experience of focusing a wide angle M12 lens on the Mobius where I would usually set the primary point of focus a few meters away and expect the depth of field to extend outwards towards infinity. My practice now is to point the camera out my office window towards some trees and shrubs on my property using a 15 foot USB cable connecting the camera to my computer in web cam mode over at my desk.

With the varifocal in telephoto "mode" it took some trial and error and a bit of time getting used to the lens before I could discover the depth of focus the lens was capable of and how to optimize it for this particular purpose. It's a bit hard to tell from your screen shots but I'm suggesting that you "might" be able to tweak the focus a bit here by doing the same thing. Of course, your experience with the fixed focal length lenses may be entirely different than working with a varifocal.
 
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TonyM

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The focus seems like it might be "slightly" off on a few of the 4mm and 6mm screen shots. I noticed a similar phenomenon with my 2.8-12mm varifocal lens at times. When that lens was set for the longest telephoto performance (10-12mm) I learned that if I set the primary focus point some 50 or more feet away I could optimize the focus from about 10 feet from my front bumper all that way out to cars in the distance. I found focusing a telephoto M12 lens (at least my varifocal, at any rate) to be different than my typical experience of focusing a wide angle lens M12 lens on the Mobius where I would usually set the primary point of focus a few meters away and expect the depth of field to extend outwards towards infinity. My practice now is to point the camera out my office window towards some trees and shrubs on my property using a 15 foot USB cable connecting the camera to my computer in web can mode over at my desk.

With the varifocal in telephoto "mode" it took some trial and error and a bit of time getting used to the lens before I could discover the depth focus the lens was capable of and how to optimize it for this particular purpose. It's a bit hard to tell from your screen shots but I'm suggesting that you "might" be able to tweak the focus a bit here by doing the same thing. Of course, your experience with the fixed focal length lenses may be entirely different that working with a varifocal.
I have found it difficult to focus these lenses, although that is in part because it's the first time I've done it. The F1.2 seems to have a fairly shallow depth of field, and it takes only a very small turn in the holder to drift out of focus. By comparison, focusing the 130deg lens D was much easier. I think I set these to focus about 5m away on a fence in my garden, but the front of the car is definitely looking sharp in the 4mm screenshots so it's not quite right.
 

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I have found it difficult to focus these lenses, although that is in part because it's the first time I've done it. The F1.2 seems to have a fairly shallow depth of field, and it takes only a very small turn in the holder to drift out of focus. By comparison, focusing the 130deg lens D was much easier. I think I set these to focus about 5m away on a fence in my garden, but the front of the car is definitely looking sharp in the 4mm screenshots so it's not quite right.
Yes, the shallower depth of field on the telephoto is partly what I'm talking about. Focusing the varifocal is difficult, fussy and requires a bright sunny day along with a sharp image on screen. (and a light touch while adjusting). For me, web cam mode is vital for focusing the Mobius, especially with a telephoto. Plugging the camera into an HDTV in AV mode works but I found it much more of a challenge to achieve critical focus.

One trick that has worked for me is to always focus on the same set of objects outside my window, an apple tree and a privet hedge. Each time I focus, I choose a particular branch or spot on the hedge and pick a point to focus on in front or behind. Somehow the more I've done this the more I know what to expect when I capture vehicles out on the highway. A few times early on I focused on objects closer in and ended up with nice sharp images near my front bumper and out of focus cars out on the road in front of me. Eventually, I found the sweet spot.
 
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Night time testing of the F1.2 Mobius lenses. This time with an individual frame and a compilation video.

Note that it was raining, so there is more glare than normal due to the wet windscreen.

A reminder of the settings:
Mobius 1 @ 1080p30, WDR on, 4mm F1.2 lens
Mobius 1 @ 1080p30, WDR on, 6mm F1.2 lens
A119v2 @ 1440p30, WDR on

A119

4mm F1.2

6mm F1.2


2min compilation video of all three cameras, followed by 2min full-frame of the 4mm then 6mm lenses

So far I prefer the 6mm to the 4mm lens for its extra reach as a second camera. With a sturdy mount there's less camera shake than I was expecting. These F1.2 lenses definitely give a much brighter night video than any of the standard lenses.
Thank you for the comparison, expecting delivery of the same 4 and 6mm by Treeye. Now it's between this 6mm and the other 8 and 12mm I should also be receiving soon.
 

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Thank you for the comparison, expecting delivery of the same 4 and 6mm by Treeye. Now it's between this 6mm and the other 8 and 12mm I should also be receiving soon.
I'm planning to order these two lenses too. :hungry: The 6mm will be front facing and the 4mm will be experimental as a side camera replacement lens with the idea that the ƒ/1.2 would improve imaging through the tinted glass on my rear windows.

Which 8mm and 12mm lenses did you order and what apertures do they have? On the Mobius as we see here, the 6mm ƒ/1.2, which is designed specifically for a 1/2.5" sensor is providing a FOV quite similar to my 12mm ƒ/1.4 varifocal on the Mobius because the varifocal is specifically designed for a 1/3" sensor. It will be interesting to see the results from your 8mm and 12mm, assuming you plan to install them on the Mobius 1.

@dirkzelf should be receiving a nice commission from the vendor for selling all these lenses! :D
 

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I'm planning to order these two lenses too. :hungry: The 6mm will be front facing and the 4mm will be experimental as a side camera replacement lens with the idea that the ƒ/1.2 would improve imaging through the tinted glass on my rear windows.

Which 8mm and 12mm lenses did you order and what apertures do they have? On the Mobius as we see here, the 6mm ƒ/1.2, which is designed specifically for a 1/2.5" sensor is providing a FOV quite similar to my 12mm ƒ/1.4 varifocal on the Mobius because the varifocal is specifically designed for a 1/3" sensor. It will be interesting to see the results from your 8mm and 12mm, assuming you plan to install them on the Mobius 1.

@dirkzelf should be receiving a nice commission from the vendor for selling all these lenses! :D
8mm is 1/2.7, f/1.6 and 12mm is 1/2.5, f/1.8

8's probably going to look like 9 or 10mm, the 12mm one probably in the range of 14-16 ( I'm guessing). Curious to see how they look mounted.

https://www.aliexpress.com/store/product/cctv-cameras-lens-8mm-M12-Lens-3Mega-pixel-High-resolution-CCTV-CAMER-LENS-10pcs/215179_32433947658.html

https://www.aliexpress.com/store/product/ount-1-1-8-inch-f1-8-12mm-ir-cut-filter-m12-lens/215179_32680519689.html

These will replace the A2 lens on my 2nd Mobius.
 
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Dashmellow

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8MM is 1/2.7, f/1.6 and 12MM is 1/2.5, f/1.8

8's probably going to look like 9 or 10mm, the 12mm one probably in the range of 14-16 ( I'm guessing). Curious to see how they look mounted.

https://www.aliexpress.com/store/product/cctv-cameras-lens-8mm-M12-Lens-3Mega-pixel-High-resolution-CCTV-CAMER-LENS-10pcs/215179_32433947658.html

https://www.aliexpress.com/store/product/ount-1-1-8-inch-f1-8-12mm-ir-cut-filter-m12-lens/215179_32680519689.html

These will replace the A2 lens on my 2nd Mobius.
Thanks!

Looks interesting! I'm curious to see the actual FOV you end up with on both lenses.
 

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Thanks!

Looks interesting! I'm curious to see the actual FOV you end up with on both lenses.
I have a feeling that the 12mm will turn out be a little too narrow/zoomed in due to the crop factor. Let's see...
 

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I have a feeling that the 12mm will turn out be a little too narrow/zoomed in due to the crop factor. Let's see...
That's what I'm thinking too. Personally, I was hoping to finds an 8mm with a ƒ/1.2 aperture but that doesn't seem to exist. From the looks of things above, the 6mm should do what I have in mind. Of course, I've got my ƒ/1.4 varifocal zoom and I'm planning to eventually install an IR cut filter on it but when you zoom a lens like that all the way to its max the effective aperture is reduced.
 

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That's what I'm thinking too. Personally, I was hoping to finds an 8mm with a ƒ/1.2 aperture but that doesn't seem to exist. From the looks of things above, the 6mm should do what I have in mind. Of course, I've got my ƒ/1.4 varifocal zoom and I'm planning to eventually install an IR cut filter on it but when you zoom a lens like that all the way to its max the effective aperture is reduced.
6mm will obviously look better due to the larger aperture but the zoom doesn't look enough from a telephoto perspective. I hope the f/1.6 on the 8mm suffices at night.
 

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6mm will obviously look better due to the larger aperture but the zoom doesn't look enough from a telephoto perspective. I hope the f/1.6 on the 8mm suffices at night.
Yeah, as I said, it will be interesting to see your results. I might just stick with my varifocal for the telephoto and go with a 4mm for the side cam and see what results I get. (There is nothing particularly wrong with the C2 lenses on the side cams actually, but you know.....:playful:) It will depend on what happens installing the IR-cut filter in the varifocal. Because the rear element on the IR is quite recessed it looks as if installing an IR cut filter might be really challenging. If it were really easy, I probably would have tried it by now. :D
 
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Yeah, as I said, it will be interesting to see your results. I might just stick with my varifocal for the telephoto and go a 4mm for the side cam and see what results I get. (There is nothing particularly wrong with the C2 lenses on the side cams actually, but you know.....:playful:) It will depend on what happens installing the IR-cut filter in the varifocal. Because the rear element on the IR is quite recessed it looks as if installing an IR cut filter might be really challenging. If it were really easy, I probably would have tried it by now. :D
f/1.2 is probably as good as it gets with lenses in this price bracket, tradeoff with the 4mm would be losing out on your overlapping coverage.

All the best with the filter.
 
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I'm interested to see what result I get with the 25mm f2.4 lens I bought. When I tried it briefly before installing the 6mm, I noticed that the colours were rather different from the 6mm and 4mm which look alike. I'm not expecting it to be much use as a dashcam, but it will be interesting to see what details I can get with it.
 

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f/1.2 is probably as good as it gets with lenses in this price bracket, tradeoff with the 4mm would be losing out on your overlapping coverage.

All the best with the filter.
If I like the 4mm it just might end up as my new rear facing lens. :)I recently sort of impulse purchased an Aukey DR-02 as a Lightning Deal on Amazon and have been testing it as a rear cam. It's a nice camera, especially for the 50 bucks I paid but it just can't touch the Mobius during the day. This is not the thread to discuss that cam though so I'll talk about it elsewhere, but in any event, the experience got me thinking about tweaking my Mobi.
 
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If I like the 4mm it just might end up as my new rear facing lens. :)I recently sort of impulse purchased an Aukey DR-02 as a Lightning Deal on Amazon and have been testing it as a rear cam. It's a nice camera, especially for the 50 bucks I paid but it just can't touch the Mobius during the day. This is not the thread to discuss that cam though so I'll talk about it elsewhere, but in any event, the experience got me thinking about tweaking my Mobi.
I was thinking of going with the 6mm up front and 4mm rear facing - at least that was the plan when I bought them. I'll need to make a stiffer mount for the rear camera though.
 

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I was thinking of going with the 6mm up front and 4mm rear facing - at least that was the plan when I bought them. I'll need to make a stiffer mount for the rear camera though.
I use some DIY mounts I built a year and a half ago for my side and rear cams (which are still holding up great!) and I know @harsh has some very nice 3D printed ones made to specific angles....(forgot where he sourced them but he can chime in on that) - Banggood also has some decent 3D printed mounts. Anyway, maybe these options might offer some DIY inspiration? :)
 

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