Mobius Varifocal Zoom IR

[Dashmellow]

Better yet, I can link to the listing (maybe this will help others avoid this product).

https://www.amazon.com/gp/B08Z4BRP4N

Did a little research. Apparently, there is a 5MP ƒ1.4 - 2.8mm to 12mm Varifocal lens available now, so it's legit. It's something new, so you should be fine. The old version was 3MP (which is still available).

Remove your current lens from your camera, close the housing and screw in the new varifocal as far as it will go until it feels tight and secure and see what happens!

 

[dchang0]

Did a little research. Apparently, there is a 5MP ƒ1.4 - 2.8mm to 12mm Varifocal lens available now, so it's legit. It's something new, so you should be fine. The old version was 3MP (which is still available).

Remove your current lens from your camera, close the housing and screw in the new varifocal as far as it will go until it feels tight and secure and see what happens!

Sadly it's not going to work. Here are some photos that show what's going on. I think that it simply exceeds the focal length range of this particular lens. And the lens is probably correctly labeled (2.8mm to 12mm is probably being exceeded in all cases because the lens is so far out of the lens holder),

It would probably work with the 6mm-22mm varifocal.... Obviously, I don't want to grind anything, especially as original Mobius 1 parts get harder to come by over time.

 

[dchang0]

As it is now, I might be able to get a lens holder that has a base of 2mm that would fit between the two plastic lips (no grinding of the first plastic lip necessary). I measured the distance between the two plastic lips and it's 3.39mm. If the lens holder has a 2mm tall rectangular base and the sensor PCB is 1mm to 1.39mm thick, it should fit fine.
If I can find such a lens holder, it just means more time waiting for parts to get here from China (AliExpress), but it would be the safest way to go and still use this lens. Or I can buy the 6mm-22mm varifocal, which will probably work with everything unmodified.

The Mobius 1 is truly versatile--most other dashcams would absolutely require irreversible modifications. At least I have some chance of not modifying anything if I just buy the right parts.

 

[Dashmellow]

As it is now, I might be able to get a lens holder that has a base of 2mm that would fit between the two plastic lips (no grinding of the first plastic lip necessary). I measured the distance between the two plastic lips and it's 3.39mm. If the lens holder has a 2mm tall rectangular base and the sensor PCB is 1mm to 1.39mm thick, it should fit fine.
If I can find such a lens holder, it just means more time waiting for parts to get here from China (AliExpress), but it would be the safest way to go and still use this lens. Or I can buy the 6mm-22mm varifocal, which will probably work with everything unmodified.

The Mobius 1 is truly versatile--most other dashcams would absolutely require irreversible modifications. At least I have some chance of not modifying anything if I just buy the right parts.

Did a little research. Apparently, there is a 5MP ƒ1.4 - 2.8mm to 12mm Varifocal lens available now, so it's legit. It's something new, so you should be fine. The old version was 3MP (which is still available).

My apologies! Apparently, I was mistaken when I said that the 5MP lens you purchased on Amazon was legit. It seems that there is indeed a 5MP Variocal 2.8mm-12mm lens available but it is NOT an M12 lens that can fit the standard lens holder on a Mobius or typical dash cam. I missed an important detail about the 5MP 2.8mm-12mm lenses I found at Treeye and elewhere. It is an M14 lens, not an M12. That means the lens barrel is 14mm in diameter rather the 12mm, so it would not fit the lens holder. After some further research, I am unable to find a 5MP 2.8-12mm varifocal lens anywhere that has a M12 mount. All I am seeing are the 3MP versions. I think the seller on Amazon may be misrepresenting what he is selling. Sorry I missed that detail last night.

I would recommend returning the lens and getting the 5MP 6mm-22mm lens. It is overall a much sharper and better lens with greater useful range than the 3MP.

It may or may not work with your current lens holder. I think you may still need to obtain a longer lens holder. Either way, here's what you need to know.

With the measurements you have already made it sounds like you are on the right track.

As you know, you need to have the rear element of the lens at the proper distance from the sensor to achieve focus. Earlier, I suggested that this should be pretty easy because a varifocal lens can adjust for this requirement unlike a fixed focal length lens like what we usually have in our dash cams. For example, the back focal length range on the M14 version of the 5MP 2.8mm-12mm lens is listed as between 7.15-12.75mm depending on how you set the focus. Obviously, if you can't get the rear element somewhere in the range where it will focus, it won't work. So, the specification you need to be aware of is called BFL (back focal length) This is the optical focal distance between the rear of the lens and the sensor. The other relevant spec is the MBF (minimum back focus) which is the physical distance between the rear element of the lens and the sensor. Not every vendor lists these specs completely or at all. Most don't seem to mention MBF but BFL should tell you what you need to know.

The optical BFL for the 5MP 6mm-22mm lens is listed as 6.4mm. (no range is listed) The BFL for the 3MP 2.8-12mm varifocal lens you apparently purchased is listed as 6.39mm, so virtually identical. Again, this suggests that you may still have problems unless you get a longer lens holder or make some other modification.

 

[dchang0]

.... I think the seller on Amazon may be misrepresenting what he is selling. Sorry I missed that detail last night.

I would recommend returning the lens and getting the 5MP 6mm-22mm lens. It is overall a much sharper and better lens with greater useful range than the 3MP.

It may or may not work with your current lens holder. I think you may still need to obtain a longer lens holder. Either way, here's what you need to know.

With the measurements you have already made it sounds like you are on the right track.

As you know, you need to have the rear element of the lens at the proper distance from the sensor to achieve focus. Earlier, I suggested that this should be pretty easy because a varifocal lens can adjust for this requirement unlike a fixed focal length lens like what we usually have in our dash cams. For example, the back focal length range on the M14 version of the 5MP 2.8mm-12mm lens is listed as between 7.15-12.75mm depending on how you set the focus. Obviously, if you can't get the rear element somewhere in the range where it will focus, it won't work. So, the specification you need to be aware of is called BFL (back focal length) This is the optical focal distance between the rear of the lens and the sensor. The other relevant spec is the MBF (minimum back focus) which is the physical distance between the rear element of the lens and the sensor. Not every vendor lists these specs completely or at all. Most don't seem to mention MBF but BFL should tell you what you need to know.

The optical BFL for the 5MP 6mm-22mm lens is listed as 6.4mm. (no range is listed) The BFL for the 3MP 2.8-12mm varifocal lens you apparently purchased is listed as 6.39mm, so virtually identical. Again, this suggests that you may still have problems unless you get a longer lens holder or make some other modification.

Wow, thanks for the big knowledge-drop! I didn't know about the term "Back Focal Length," though I wondered about the same concept when fiddling with the lens and the holder. I was wondering exactly where the specified focal length was actually measured from along the center axis of the lens assembly.

Given the BFL of 6.39mm or 6.4mm, that raises suspicions about the lens and whether I am going to have to cut the case to get this particular lens to work. I'll do some measurements and mark up some photos to show you what I'm suspicious about.

 

[Dashmellow]

Wow, thanks for the big knowledge-drop! I didn't know about the term "Back Focal Length," though I wondered about the same concept when fiddling with the lens and the holder. I was wondering exactly where the specified focal length was actually measured from along the center axis of the lens assembly.

Given the BFL of 6.39mm or 6.4mm, that raises suspicions about the lens and whether I am going to have to cut the case to get this particular lens to work. I'll do some measurements and mark up some photos to show you what I'm suspicious about.

FWIW, both the 2.8mm-12mm lens and the 6mm-22mm have worked perfectly in two different Mobius cameras without any sort of modification at all. I just screw them in all the way until they are snug to the case. I believe that is the case with everyone else who has installed one of these lenses. Considering that there are several different lens holders that came with various Mobius 1 cameras I am puzzled that you are having so much trouble. When you get the 5MP 6mm-22mm ƒ/1.6 try it and see what happens and go from there. There's a reasonable chance you won't need to do anything but screw it in and focus the things.

 

[dchang0]

FWIW, both the 2.8mm-12mm lens and the 6mm-22mm have worked perfectly in two different Mobius cameras without any sort of modification at all. I just screw them in all the way until they are snug to the case. I believe that is the case with everyone else who has installed one of these lenses. Considering that there are several different lens holders that came with various Mobius 1 cameras I am puzzled that you are having so much trouble. When you get the 5MP 6mm-22mm ƒ/1.6 try it and see what happens and go from there.

Thanks for confirming that. I have been wondering all this time whether anyone else is having the same problems I'm having.

After I take some measurements of the lens holder and 2.8-12mm that I currently have on hand, it should become clear which part(s) is causing the trouble.

 

[Dashmellow]

Wow, thanks for the big knowledge-drop! I didn't know about the term "Back Focal Length,"

There is another term that might interest you especially if you clicked on the links to AliExpress in my post above. That would be "Flange focal distance" which on THIS link was called "Flange Back Focal Length".

You can read about it in my post to a different Mobius Zoom lens thread posted by another member. I bring it up because it has some bearing on your efforts to get your camera and varifocal lens to focus properly and because I think the thread may be of interest to you under the circumstances. See also: https://en.wikipedia.org/wiki/Flange_focal_distance

See: Mobius Zoom Lens

 

[dchang0]

There is another term than might interest you especially if you clicked on the links to AliExpress in my post above. That would be "Flange focal distance" which on THIS link was called "Flange Back Focal Length".

You can read about it in my post to a different Mobius Zoom lens thread posted by another member. I bring it up because it has some bearing on your efforts to get your camera and varifocal lens to focus properly and because I think the thread may be of interest to you under the circumstances. See also: https://en.wikipedia.org/wiki/Flange_focal_distance

See: Mobius Zoom Lens

Hmm. Based on the drawing and the specified 13.5mm, it does seem that currently, photo #2 (where the lens is 90% screwed into the lens holder) is correct. The approximate distance of the flange to the sensor is about 12.5mm to 13.0mm. Thus, I think I am indeed going to have to grind out the first plastic lip so that the lens holder can slide forward to the second lip.

I am working on drawing the situations in 2D in Inkscape with measurements to make it clear.

What I suspect right now is that most everyone else is able to position their lens holder forward at plastic lip 2 without having to grind anything out.

 

[Dashmellow]

Hmm. Based on the drawing and the specified 13.5mm, it does seem that currently, photo #2 (where the lens is 90% screwed into the lens holder) is correct. The approximate distance of the flange to the sensor is about 12.5mm to 13.0mm. Thus, I think I am indeed going to have to grind out the first plastic lip so that the lens holder can slide forward to the second lip.

I am working on drawing the situations in 2D in Inkscape with measurements to make it clear.

What I suspect right now is that most everyone else is able to position their lens holder forward at plastic lip 2 without having to grind anything out.

Why not wait until you get the new lens and see what happens before you do anything radical? It might just work.

How old is your Mobius? Maybe you have the old case and module which has different slots for the lens module?

 

[dchang0]

Why not wait until you get the new lens and see what happens before you do anything radical? It might just work.

How old is your Mobius? Maybe you have the old case and module which has different slots for the lens module?

Good point. No need to grind anything until I get the new lens...

Re: "different slots" I think that this is probably what's going on. Either that, or the newer lens holder allows the owner to choose either of the two existing slots in the camera housing without grinding.

My Mobius 1 is pretty old. I am searching for the receipt but my estimate is that I bought it in 2015 to 2017.

I am absolutely certain I don't have the metal lens holders of the very old Mobius 1 models. I've seen photos of those and mine looks nothing like them. I am pretty sure it's FRP.

 

[dchang0]

Okay, here are the line drawings that show my findings and measurements of the Flange Back Focal Length in the two Lip positions.

 

[dchang0]

This might be the optimal solution, or close to it, if I can find a lens holder whose square base fits between Lips 1 and 2. FBFL ends up being around 10.51mm.




-----

At this point, I think the best solutions are:

1) Get an 18mm lens holder with square base of 2mm and cylindrical portion of about 8.25mm. It would look like it was made for fitting between Lips 1 and 2. Hard to do this since so few lens holder sellers actually specify all the pertinent dimensions of their lens holders.

2) Get another camera housing, hoping that the lips are different. This could be made more certain if other Mobius 1 owners check their camera housings to see how the lips are spaced.

3) Give up on the varifocal lens entirely and buy another A2 lens module or C2 lens module. No cutting required, and everything should just work. There is the slight possibility that if my camera housing is too different, the new modules will not fit inside, but that is unlikely.

 

[dchang0]

Had to update the numbers because I realized I was measuring from the shoulder of the lens holder and not the sensor. Also corrected the lens' specified FBFL, which is 13.5mm. Oops.

 

[Harsh]

C2 and A2 housing

 

[dchang0]

C2 and A2 housing

View attachment 59350

Whoa, thanks so much! I definitely have the one in the bottom of the photo. The one in the top of the photo where the two lips are roughly evenly spaced should allow me to use my existing lens holder in either "compartment."

Given that I need to replace my camera housing anyway due to the plastic tabs breaking off from an expanding battery, what I'll do now is try to find the evenly-spaced housing.

 

[Harsh]

Whoa, thanks so much! I definitely have the one in the bottom of the photo. The one in the top of the photo where the two lips are roughly evenly spaced should allow me to use my existing lens holder in either "compartment."

Given that I need to replace my camera housing anyway due to the plastic tabs breaking off from an expanding battery, what I'll do now is try to find the evenly-spaced housing.

You could slice off the extra bits using a blade. I've mutilated a few Mobius housings to fit different lenses.

If you do, don't buy too many. The two I just clicked a photo of have gone sticky on the outside. Were inside the bubble wrap packaging they came in for over a year.

 

[dchang0]

You could slice off the extra bits using a blade. I've mutilated a few Mobius housings to fit different lenses.

If you do, don't buy too many. The two I just clicked a photo of have gone sticky on the outside. Were inside the bubble wrap packaging they came in for over a year.

Thanks! I just realized that there's not really any way to specify "I want a C2 housing" to the parties currently selling spare housings. I'd have to email them the photo you posted and point at the top one and say "do you sell these?" Cutting the broken case I have might be the best choice because it's already broken--if I mess up, oh well, I was gonna replace it anyway.

Thanks for the warning. Yeah, that's a terrible problem with nearly all plastic products with rubberized coatings. You should have seen what happened to the rubberized parts in our car, especially the door handles. They became gooey messes. I eventually had to replace all the rubberized plastic parts because it was so gross to touch the goo. On my current Mobius 1 housing, I had to scrub the goo off with 99% isopropyl alcohol.

 

[Harsh]

Thanks! I just realized that there's not really any way to specify "I want a C2 housing" to the parties currently selling spare housings. I'd have to email them the photo you posted and point at the top one and say "do you sell these?" Cutting the broken case I have might be the best choice because it's already broken--if I mess up, oh well, I was gonna replace it anyway.

Yeah, that's a terrible problem with nearly all plastic products with rubberized coatings. You should have seen what happened to the rubberized parts in our car, especially the door handles. They became gooey messes. I eventually had to replace all the rubberized plastic parts because it was so gross to touch the goo.

The culprit in this case is the bubble wrap they were sitting in. A couple of housings not inside the wrap are fine, so is the Maxi housing in a different bubble wrap.

I know what you mean though. Have had it happen to two or three pairs of scissor handles over the years.

 

[dchang0]

The culprit in this case is the bubble wrap they were sitting in. A couple of housings not inside the wrap are fine, so is the Maxi housing in a different bubble wrap.

I know what you mean though. Have had it happen to two or three pairs of scissor handles over the years.

Yeah, not being a chemist or materials engineer, I suspect that these rubberized coatings stay stable until they cross some kind of tipping point, and then they just rapidly disintegrate. It could be temperature, or maybe the rubber was off-gassing some kind of stabilizer for years, or maybe it's UV light--it's probably different for all of these rubberized coatings.

In my polyurethane coated backpacks and tents, the polyurethane disintegrated into a gooey mess too, though from what I read it's water/humidity that causes them to fail (even though they are applied to be a waterproof coating!).