Mobius Telephoto Dashcam

[Harsh]

8mm & 12mm - Sunny

 

[TonyM]

Focus looks to be where it was set. 8 and 12 are a little jumpy due to the overall weight. Need to add a fresh layer of EVA foam to the mounting plate.

I've just stopped using my mounting plate with 3 Mobius cameras together on a single helmet mount, as I was getting too much vibration in the video.

 

[TonyM]

The ƒ/1.2 lenses don't give you too much room for error with the shallow depth of field they provide. Sometimes, I find that what looks good when I'm focusing doesn't look quite so good when I go to shoot actual video and so then I'll have to go back and make an adjustment.

I found just the same with my 6mm f1.2. It can look very good one day, but out of focus the next. I think the act of tightening the set screw affects the focus too. These fast lenses are potentially very useful, but they're a pain to work with.

 

[Harsh]

I've just stopped using my mounting plate with 3 Mobius cameras together on a single helmet mount, as I was getting too much vibration in the video.

The fit between the helmet mount, bridge plate and both the cameras is super tight. A layer of EVA foam should do the trick. Let's see.

 

[TonyM]

I have to disagree with your approach here. Having to modify the case on a Mobius is only a "common problem" if you are in the habit of purchasing lenses that are not compatible with the camera in the first place. While I would certainly be willing to modify the case (or other components such as the threaded lens module barrel) on a Mobius camera if I needed to (and I have), the goal should be to install compatible lenses in the first place. I think it's fine to modify a camera if you need to for a specific lens but I believe doing so should be the exception, not the rule.

A week ago in this thread I tried to make the case that it is best to order lenses from a knowledgeable vendor who is able to provide all the technical information you need to make an intelligent lens buying decision.

The consequences of buying from a vendor who tells you absolutely nothing about what they are selling you result in the kind of experience @jackalopephoto reported yesterday where he says, "But the 12mm lens and the 8mm lens can't focus on the Mobius. The housing blocks them before they can screw in far enough. You would have to modify the case". This is exactly the kind of outcome I was cautioning about.

If you want to install an aftermarket lens in your camera, the first thing you need to do is measure the thread depth of the lens module on your camera. In the case of the Mobius it is 12.5mm. Then add the distance from the lip of the module to the front of the camera's case. Now you how long the threaded barrel on the new lens needs to be in order for it to screw into the barrel as far as required. As long as the lens is narrow enough but with a long enough threaded barrel, you don't need to worry about the size of the hole in the case.

View attachment 36034

I first encountered and learned about this issue several years ago when installed a different lens into my old G1WH. The first three lenses I tried wouldn't work because of the thread depth on both the lens and the module barrel. While I did have to make an alteration the camera's housing, even without the front of the case even on the camera three different lenses would not work at all because I couldn't screw them far enough into the barrel to achieve focus because the threaded part of the lens barrels were not long enough. They couldn't screw in far enough for those particular lenses BFL requirements. I discovered that on many M12 lenses the threads do not go all the way up the full length of the barrel and of course some lenses don't have very long barrels, so now when I consider an alternative lens for a camera that's one of the first things I look for.

The basic (installation) specs to look for when shopping for a lens are BFL, (back focal length) MBF (minimum back focus), and lens thread depth. These specs work in concert with the module's threaded lens barrel. Obviously the specific size sensor and all the other specs are important to know but the BFL, MBF and thread depth are the specs you need to know regarding whether the lens can even be installed and focused. This is critical. If these numbers are not right, look elsewhere for an appropriate lens to fit your camera; there are literally hundreds of lenses to chose from. The way I see it, if the specialized lens you purchased requires you to permanently alter the housing of the camera, then you've probably chosen the wrong lens. Obviously, if this happens to be the only lens that will achieve the desired results, that's another story.

Treeye and Peau Productions are two examples of professional lens vendors who go out of their way to provide buyers with everything they need to know before purchase so that you end up with a compatible lens that will meet your requirements.
Peau Productions, as an action camera specialist even goes to the trouble of categorizing many of their lens offings according to their compatibility to specific cameras and like Treeye they publish all available lens specifications.

Here for example, is the information Treeye provides for the 6mm ƒ/1.2 Starlight telephoto lens. Not only do they provide all the necessary specifications to know if the lens meets your requirements they also provide a technical drawing of the lens so you know the exact physical measurements of the lens. This way you you know the thread depth on the lens along with everything else about how it will fit your camera before purchasing.

View attachment 36033

I've labeled the required fitting specs in blue.
View attachment 36032

You make a lot of good points there. It's evident that you have made mistakes previously with your G1WH that some of us are making now with our mobius cameras.

Even the 3no telephoto lenses that eletoponline365 sent to me to evaluate don't work in a regular mobius case!

Did you get your Treeye 6mm F1.2 to fit in a standard mobius case?

 

[Dashmellow]

You make a lot of good points there. It's evident that you have made mistakes previously with your G1WH that some of us are making now with our mobius cameras.

Thanks. Yes, I was familar the concept of "back focal length" long before I ever got interested in dash cams and actions cams but it was only after trying to replace M12 lenses in these camera did I find myself having to deal with the practical application of the concept in this way. I did have to deal with back focal length long ago when using a view camera but it was a question of focus and circle of coverage with a bellows that is different than a fixed, threaded lens.

Even the 3no telephoto lenses that eletoponline365 sent to me to evaluate don't work in a regular mobius case!

Sounds kind of like when Peter sent me the M2 to evaluate with the prototype lens that wobbled back and forth because the module didn't fit the case.

Did you get your Treeye 6mm F1.2 to fit in a standard mobius case?

Yes, it fits perfectly and looks quite a lot like the photos you posted in your OP to this thread. The diameter of the 6mm ƒ/1.2 lens barrel is a perfect snug fit for the lens opening in the M1 housing so it is very secure and stable.
That's where the technical lens drawing with all the detailed measurements provided by Treeye comes in handy when ordering.

 

[TonyM]

The diameter of the 6mm ƒ/1.2 lens barrel is a perfect snug fit for the lens opening in the M1 housing so it is very secure and stable.
That's where the technical lens drawing with all the detailed measurements provided by Treeye comes in handy when ordering.

Following my issues with fitting various lenses into cases, I decided to buy some digital calipers so I could take appropriate measurements before ordering any more lenses.

 

[Deleted member 37895]

I found just the same with my 6mm f1.2. It can look very good one day, but out of focus the next. I think the act of tightening the set screw affects the focus too. These fast lenses are potentially very useful, but they're a pain to work with.

I like the broad depth of field of my 6mm. I don't know what the f stop is but I'd guess about F3

 

[Harsh]

How about this - https://www.aliexpress.com/item/2pc...t-source-transparent-sealant/32813046168.html

 

[Dashmellow]

How about this - https://www.aliexpress.com/item/2pc...t-source-transparent-sealant/32813046168.html

As far as I can tell, that stuff is made for sealing luminaires, outdoor lighting fixtures, car headlights and stuff like that. When they talk about "optical lens sealant", I think "lens" in this instance means what goes onto the light fixture and not camera "lenses".

Kafuter K-5905 - "Fast Dry High-Temp RTV Silicon Sealant & Silicone Glue for Outdoor Lights"

https://kafuter.en.alibaba.com/product/658624299-801875425/Kafuter_K_5905_Fast_Dry_High_Temp_RTV_Silicon_Sealant_Silicone_Glue_for_Ourdoor_Lights.html#!

Application

(1) Bonding and waterproof sealing in LED fence protect tubes(Guardrail tube), LED surface lights and other lightings

(2) Bonding and sealing engineering-plastics, metal , glass, ceramics.

(3) Positioning, reinforcing, and moisture proof sealing electronic components in circuit board.

(4) Also, can bond in bumpers, hangers, and mirrors, seal in car lights, rear-view mirrors, and shower heads.

 

[Harsh]

As far as I can tell, that stuff is made for sealing luminaires, outdoor lighting fixtures, car headlights and stuff like that. When they talk about "optical lens sealant", I think "lens" in this instance means what goes onto the light fixture and not camera "lenses".

Came up as a suggestion while browsing through butyl rubber sealant listings.

"No solvents, corrosion, and pollution", I think they mean there isn't any corrosive fuming. If applied judiciously, should work.

 

[TonyM]

While we're on the subject of adhesives - for cameras without a set screw in the lens holder, what would you recommend for fixing a lens in place once you have achieved the correct focus?

 

[Dashmellow]

While we're on the subject of adhesives - for cameras without a set screw in the lens holder, what would you recommend for fixing a lens in place once you have achieved the correct focus?

I use a small piece of 3M VHB tape. It holds the lens in place very securely but can easily be removed for refocusing or swapping in a different lens.

 

[Dashmellow]

Came up as a suggestion while browsing through butyl rubber sealant listings.

"No solvents, corrosion, and pollution", I think they mean there isn't any corrosive fuming. If applied judiciously, should work.

I guess so. I'm stickin' with my Lazer Bond for now.

 

[Dashmellow]

While we're on the subject of adhesives - for cameras without a set screw in the lens holder, what would you recommend for fixing a lens in place once you have achieved the correct focus?

BTW, I almost forgot. Several weeks ago I went down to the local hardware store and bought some tiny hex-driven set screws ( the smallest I could find) that are extremely similar to the ones that come on the original Mobius lenses. They are not quite as small as the originals, but close. I also purchased a drill bit that is very slightly smaller than the threaded set screws. I have several spare lens module barrels and my plan is to drill slightly smaller holes using a Dremel tool and see if I can't fabricate a DIY lens locking module housing using the set screw as a thread tap. The motivation for this is my Varifocal lens that really wants a beefier threaded barrel than the one I originally mounted it in.

This project is still on the back burner at the moment but I keep eyeing my box of little parts near my desk. When I finally go to remount my Varifocal 2.8-12mm on a Mobius I'll likely get motivated to do this.

 

[Radius8]

Here's a place (and it's a great fun web site) that sells taps for tinny screws:

metric: https://www.micromark.com/Metric-Tap
standard: https://www.micromark.com/Tap-Drill_3

The Mobius set screw appears to be M2. Finding a set screw to fit may be a challenge though. Amazon has a bunch of "eye glasses screw" repair kits but that appears to be M1 to M1.6.

 

[Dashmellow]

Here's a place (and it's a great fun web site) that sells taps for tinny screws:

metric: https://www.micromark.com/Metric-Tap
standard: https://www.micromark.com/Tap-Drill_3

The Mobius set screw appears to be M2. Finding a set screw to fit may be a challenge though. Amazon has a bunch of "eye glasses screw" repair kits but that appears to be M1 to M1.6.

Thanks! That's an interesting resource.

You're right that it is difficult to find small enough grub screws to fit the Mobius. The closest I've found available so far are M3 and often you need to purchase quite a few of them or an assortment box even if you only need a couple of them.

We happen to have an amazing old school hardware store nearby where I live that has been around for 50 years+. They have a wall of small old oak drawers full of every kind of hard to find screw, nut, washer or odd part you can ever imagine and you can buy them individually. No M2 bung screws though, but still, a decent assortment almost as small.

One of the challenges I sometimes find in doing these kind of DIY projects is that some of these specialized tools like miniature thread taps can be relatively pricey and I'm reluctant to invest in a tool that I may only use once or twice for a unique low cost project like installing a set screw in a lens module.

One of the reasons I am a big fan of Banggood is that unlike any other online Chinese retailer, they specialize in DIY supplies, parts and tools and have a mind boggling inventory of stuff. For example, recently I've been purchasing a whole range of low priced but decent quality attachments and tools for my rotary tool, many of which I've never seen available elsewhere. You could spend hours clicking through all of the unique tools and parts Banggood sells ( and I have ).



They sell grub screws (set screws) too. Often you need to buy an assortment or quantity. The smallest they seem to have is M3.




I found these M2 screws and I guess they might work.




And lots of thread taps including M2.




They also have a huge selection of watch repair parts and tools which are also very useful for miniature camera projects.

 

[Radius8]

Argh... I am unable to access these sites (corporate firewall). Oh well... I guess perhaps it's for the best; productivity would have really taken a dive .

I know what you mean about having to buy a tool just for that one project. And usually it's the odd ball tool specific just for that job and that cost an exorbitant sum too ( I am looking at you Audi).

What about this here "reusable thread locker":
https://www.mcmaster.com/#threadlockers/=1bdurrj


We have this in the lab and other than being a bit messy, does what it supposed to. You can also apply a dab on the outside, overlapping the screw and the support. It would work similarly to the red or green lacquer that is sometimes used for temper evidence but remains somewhat soft.

Amazon also sells this stuff:
https://www.amazon.com/gp/B0088YEGXM

 

[Deleted member 37895]

Argh... I am unable to access these sites (corporate firewall). Oh well... I guess perhaps it's for the best; productivity would have really taken a dive .

I know what you mean about having to buy a tool just for that one project. And usually it's the odd ball tool specific just for that job and that cost an exorbitant sum too ( I am looking at you Audi).

What about this here "reusable thread locker":
https://www.mcmaster.com/#threadlockers/=1bdurrj
View attachment 36143

We have this in the lab and other than being a bit messy, does what it supposed to. You can also apply a dab on the outside, overlapping the screw and the support. It would work similarly to the red or green lacquer that is sometimes used for temper evidence but remains somewhat soft.

Amazon also sells this stuff:
https://www.amazon.com/gp/B0088YEGXM

Threadlocker usually turns to dust so I wouldn't use it for any optical equipment

 

[Dashmellow]

Argh... I am unable to access these sites (corporate firewall). Oh well... I guess perhaps it's for the best; productivity would have really taken a dive .

I know what you mean about having to buy a tool just for that one project. And usually it's the odd ball tool specific just for that job and that cost an exorbitant sum too ( I am looking at you Audi).

What about this here "reusable thread locker":
https://www.mcmaster.com/#threadlockers/=1bdurrj
View attachment 36143

We have this in the lab and other than being a bit messy, does what it supposed to. You can also apply a dab on the outside, overlapping the screw and the support. It would work similarly to the red or green lacquer that is sometimes used for temper evidence but remains somewhat soft.

Amazon also sells this stuff:
https://www.amazon.com/gp/B0088YEGXM

Why would you want to lock the threads of a set screw in a refocusable lens?

Not quite sure what you mean by "apply a dab on the outside, overlapping the screw and the support". If you are talking about using the stuff to secure a lens in place after focus, I can see where it mighty be suitable but it wouldn't be my choice for lenses like these telephotos in this thread that we've all been experimenting with since they require focus adjustments and where you might want to remove the lens entirely so another lens can be swapped in. I favor temporary, non messy locking methods like set-screws or a pliable tape.