Mobius Varifocal Zoom IR

[TonyM]

I've actually had my eye on that 6-22mm varifocal myself and in fact recently placed an order for one from Treeye. I plan to experiment with it as a dash cam lens but primarily feel it will be better suited to wildlife observation and am looking forward to sharing it with my environmental center students.

One thing to keep in mind with these varifocal for dash cam use is the aperture. With a zoom lens, the default aperture becomes smaller and smaller the more you rack the lens out to the maximum telephoto focal length so that what starts out as ƒ/1.4 or ƒ/1.6 lets much less light through the greater the magnification. The starlight lenses might be better suited for extreme telephoto use if you want good low light imaging.

I had a hunch that these varifocal lenses were not constant aperture throughout the focal range, although the Treeye listings only state a single aperture? SLR zoom lenses have markings which clearly show whether they are constant or variable aperture.

I will probably want to use a varifocal from 6mm upwards, as that is about the minimum focal length I've been happy with for a fixed telephoto lens to make it worthwhile running alongside a standard dashcam. If the 6-22 is F1.6 at 6mm, that might be better than the 2.8-12 at 6mm? On the other hand, as you mention I am not likely to want to go beyond 12mm for dashcam use. I might also remove it from the car from time to time for wildlife observation similar to how you have used yours.

I do have a fixed 6mm F1.2 starlight lens, but the clarity of its image is nowhere near as good as your 2.8-12mm lens.

 

[Dashmellow]

DSLR lenses are much more complex as they are designed to be zoomed at will during use and in actual image capture such as on video cameras, thus they have variable apertures. CCTV varifocal lenses are manual and designed to be set to a fixed focal length at a fixed aperture in a static setting.

The key word here is really ƒ/stop, or perhaps relative aperture. In other words, if you have a varifocal CCTV type lens set to 2.8mm at ƒ/1.4, the same fixed aperture lens will have an effective lens opening of (hypothetically) perhaps ƒ/4 when set to 12mm. This is because of the ratio of the fixed lens aperture diameter to the chosen focal length setting of the lens. So the aperture doesn’t actually change as you zoom, the hole stays exactly the same size, but the ratio of focal length to aperture size does.

 

[Lola]

It wouldn't hurt to ask the seller the resolution in lines per mm and the amount of distortion in the lenses. These are important, that's why you don't see them listed very often on these cheaper lenses.

 

[Dashmellow]

It wouldn't hurt to ask the seller the resolution in lines per mm and the amount of distortion in the lenses. These are important, that's why you don't see them listed very often on these cheaper lenses.

I don't disagree about the LP/mm spec but FWIW Treeye lists the 6-22mm lens as a 5MP lens so it should offer as good and perhaps much better resolution than the 3MP 2.8-12mm varifocal which has proved itself pretty capable.

 

[Dashmellow]

I agree. Really want to try a 10mm but is only available in the pinhole variety. Sometimes even the 12 looks a bit much, especially during a panning motion.

Why no try a varifocal? I find the ability to change focal lengths at will to be a real boon. I also really enjoy the ability to easily re-focus without having to open up the camera. While it's true that it makes for a bigger camera I find the size of the lens quite tolerable, all in all. Finally, with the price of the 2.8-12mm, it's hard to go wrong.

 

[TonyM]

Do I remember that you changed your Mobius lens holder to accommodate the varifocal lens? I have one original M1 with a metal lens holder. The others are the more recent variety with plastic holders that have shorter barrels.

 

[Dashmellow]

Do I remember that you changed your Mobius lens holder to accommodate the varifocal lens? I have one original M1 with a metal lens holder. The others are the more recent variety with plastic holders that have shorter barrels.

Yes, I did. I happened to have some beefy FRP lens holders sent to me with some alternative lenses when I was testing another camera (0906) and decided to try one. As I recall I was using one of my old metal Mobius lens holders that had a hairline crack in it. I think your older ones should be ok so you can start there and change to something else if necessary. The big varifocal lens does put a lot of extra stress on the lens holder but it gets support from the camera housing.

 

[Lola]

Yes, I did. I happened to have some beefy FRP lens holders sent to me with some alternative lenses when I was testing another camera (0906) and decided to try one. As I recall I was using one of my old metal Mobius lens holders that had a hairline crack in it. I think your older ones should be ok so you can start there and change to something else if necessary. The big varifocal lens does put a lot of extra stress on the lens holder but it gets support from the camera housing.

I'm assuming the Varifocal lens is longer out of the case then normal, has this caused you any problems in mounting the camera to the windshield relative to camera length?

 

[Dashmellow]

I'm assuming the Varifocal lens is longer out of the case then normal, has this caused you any problems in mounting the camera to the windshield relative to camera length?

No, mounting hasn't really been a problem at all. I used one of the DIY mounts I made two years ago and it's worked out quite well. I had only one minor issue which was that I couldn't mount the varifocal equipped Mobius as close to my other front facing dash cam as I wanted to because the Mobius needs enough room for the varifocal to clear the other camera when you screw or unscrew it from the ball joint mount without having to change it's adjustment each time.

(This is an older photo. Since then I was able to move the camera a little closed to the GC than you see it here.)


The DIY mounts I made were all created with parts I used from the standard generic Chinese ball joint mount on the left of the photo below which you can buy on eBay and elsewhere for about 2 bucks. That mount should work fine to mount a varifocal equipped Mobius to a windshield without any modification if anyone is thinking of using their Mobius with one of these varifocals.

 

[Harsh]

Personally, I don't ever permanently glue M12 lenses in place. You never know when you may want to re-purpose a lens somewhere down the line, swap lenses or (heaven forbid) refocus. I always use something secure but reversible. But yes, I guess if you want to glue your lenses permanently into their holders UV cement should work very well.

Glue gun?

The 8mm is held securely by the locking screw but can't say the same for the 12mm. I've received the locking rings, will those be enough?

 

[Dashmellow]

Glue gun?

The 8mm is held securely by the locking screw but can't say the same for the 12mm. I've received the locking rings, will those be enough?

I've never used locking rings so I don't know. I plan to order to some play with but for the most part I don't think there is enough room to use one on the lenses I have for the Mobius since the ring would have to go inside the case where I don't believe there is enough clearance. Don't know really, which is why I will be ordering some.

 

[Lola]

No, mounting hasn't really been a problem at all. I used one of the DIY mounts I made two years ago and it's worked out quite well. I had only one minor issue which was that I couldn't mount the varifocal equipped Mobius as close to my other front facing dash cam as I wanted to because the Mobius needs enough room for the varifocal to clear the other camera when you unscrew it counterclockwise from the ball joint mount without having to change it's adjustment each time.

(This is an older photo. Since then I was able to move the camera a little closed to the GC than you see it here.)
View attachment 37785

The DIY mounts I made were all created with parts I used from the standard commercial ball joint mount on the left of the photo below which you can buy on eBay and elsewhere for about 2 bucks. That mount would work fine to mount a varifocal equipped Mobius to a windshield without any modification if anyone is thinking of using their Mobius with one of these varifocals.

View attachment 37786

The one with the angle barrel on the (3rd) mount, is that one you modified the barrel or can you buy the angled barrel ?

Whoops, I see what you did now, very ingenious, hard to believe Joovue screwed you like that, it just wasn't right!!!
Thanks for the information.

 

[Dashmellow]

The one with the angle barrel on the (3rd) mount, is that one you modified the barrel or can you buy the angled barrel ?

All three mounts the arrow is pointing toward on the right of the above photo are DIY. The one on the far left of the photo is a Chinese generic mount you can buy from many sources on the internet.

I understand that a plastic mount very similar to the curved shaft one I made (out of copper) is or was available but I have no idea where you can find one these days.

 

[TonyM]

I use that generic Chinese mount for my Mobius testing rig - it is very sturdy even with 5 cameras attached. With a telephoto lens installed, the top side cameras just clear the glass when I spin the whole assembly on/off the mount, so there should be plenty of space for a single camera and a varifocal lens attached to the mount directly.

 

[Dashmellow]

Whoops, I see what you did now, very ingenious, hard to believe Joovue screwed you like that, it just wasn't right!!!

I don't know whether JooVuu really screwed me in regard to my mount concept or not but Dan has proven himself to be his own worst enemy as evidenced by his poor attitude, condescension and disingenuousness towards his customers who have all been left in the lurch. Not that this comes as a surprise to anyone who was paying attention here on DCT before he abandoned ship leaving all passengers on board.

 

[TonyM]

Varifocal lenses ordered
One for cars
One for wildlife

 

[Dashmellow]

Glue gun?

The 8mm is held securely by the locking screw but can't say the same for the 12mm. I've received the locking rings, will those be enough?

I just realized I forgot to respond to the Glue gun question in your post.

I think it might be worth a try assuming the hot melt glue can be peeled off easily enough when you want to swap lenses again. This might even work with a tiny glob of UV cement too. I think it's worth experimenting with, maybe on an old spare camera lens and mount or something.

My go-to method has been to use a small piece of 3M VHB tape where the lens threads meet the mount. This holds the lens securely in focus for most installations but allows for easy removal.

 

[Harsh]

Glue gun?

The 8mm is held securely by the locking screw but can't say the same for the 12mm. I've received the locking rings, will those be enough?

I just realized I forget to respond to the Glue gun question in your post.

I think it might be worth a try assuming the hot melt glue can be peeled off easily enough when you want to swap lenses again. This might even work with a tiny glob of UV cement too. I think it's worth experimenting with, maybe on an old spare camera lens and mount or something.

My go-to method has been to use a small piece of 3M VHB tape where the lens threads meet the mount. This holds the lens securely in focus for most installations but allows for easy removal.

I do have a couple of dispensable mounts and lenses that I could experiment with. Thank you.

 

[Dashmellow]

I do have a couple of dispensable mounts and lenses that I could experiment with. Thank you.

Me too. I'm going to try a teeny, weeny little blob of UV cement and see if it can be removed without damage. It's basically just photo setting plastic resin, so maybe it can just pop off in one piece?

 

[TonyM]

@Dashmellow @Harsh
Did you try the UV cement on a lens & holder yet?

My UV cement and both 2.8-12mm and 6-22mm varifocal lenses arrived this morning