Mobius Lens Hood

russ331

russ331

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Dash Cam
Mobius B (x2) & A119
Posted today at http://www.rcgroups.com/forums/showpost.php?p=29405197&postcount=11413 ...

"I have cracked lenses (from Mobius falling on hard surfaces from a distance...) and there have been no visible problems with the image. The wide angle lens is less protected andcan be damaged easily (as shown in this thread) .

I have a hood to protect wide angle lens that does help. The model can be downloaded from this link or if you can't print it yourself you can get it printed."

Mobius with Lens Hood II.jpg

Thought this may be of interest here.
 
That looks very interesting. I've experimented with lens hoods on other dash cams with good success but the Mobius has been challenging in regard to a lens hood. I'm wondering about the FOV and vignetting on this one but I have to assume that the guy worked it out and the mount is rather clever.
 
It seems more of a protection use rather than glare. It seems rather short
 
GJHS said:
It seems more of a protection use rather than glare. It seems rather short
Click to expand...

If it were any longer it would likely vignette the lens. With a wide angle lens you need a "wide angle" lens shade.
 
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Would be good to see this as something which could be printed onto a standard sheet of paper & transferred to (for example) sugru or similar air dry moulding substance - or even printed out & then cut out of a sheet of plastic (like a shampoo bottle etc).
Back in the day I used to make sunshields for my instrument cluster out of a washing up liquid bottle and some black tape (to match the rest of the cowl)
 
I like the look of that stuff.
If the mobius is mounted in its cradle than the shield would be placed over the top of the cradle?
A second, similar, piece could be attached to the bottom (as mounted) of the camera to project out & maybe shield the lens from dash reflections?
 
sludgeguts said:
I like the look of that stuff.
If the mobius is mounted in its cradle than the shield would be placed over the top of the cradle?
A second, similar, piece could be attached to the bottom (as mounted) of the camera to project out & maybe shield the lens from dash reflections?
Click to expand...


Yes, that's what I was thinking anyway. Would need a bit of experimenting to get the correct length protrusion, and you'd want to get an angle on the top and bottom so that they diverge away from each other - otherwise I think you'd cut off too much sky and too much ground.

Or I suppose you might get super extra mega widescreen (wider than 16:9 anyway).
 
Well, a couple of sheets for a few pence - it's got to be worth a punt.
 
JakeBlade said:
Yes, that's what I was thinking anyway. Would need a bit of experimenting to get the correct length protrusion, and you'd want to get an angle on the top and bottom so that they diverge away from each other - otherwise I think you'd cut off too much sky and too much ground.

Or I suppose you might get super extra mega widescreen (wider than 16:9 anyway).
Click to expand...

A handy way to test out the FOV limits for crafting a lens hood for the Mobius (and other dash cams) is to use the camera in web cam mode on your computer. You can simply move a finger back and forth until you see it enter the FOV and make note of the spot to extend your lens hood for it be at its maximum depth and coverage without vignetting. If you want to get fancy you can lay the camera down on a protractor and a piece of paper when you test in web cam mode and mark the exact angle and length needed for the lens hood coverage. It's kind of fun and interesting to do this because you can measure the angle in degrees of the real world FOV your lens is providing.

I have crafted lens hoods for several dash cams, such as this one for a GT300 made from a 35mm film canister and this one for a GT680W. I have found the Mobius much more challenging to fit with a practical lens hood. The FOV and design of the wide (B) lens is such that the hood needs to be so shallow to avoid vignetting as to be almost not worth it. However any lens hood, even a very shallow one will be a benefit, especially when the sun is coming from a steep oblique angle.
 
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JakeBlade said:
In a moment of weakness/boredom, I ordered some last night. Will let you know how I get on with it.
Click to expand...
Like I said, a few pence for a sheet...
I also ordered - should be here shortly.
 
Dashmellow said:
A handy way to test out the FOV limits for crafting a lens hood for the Mobius (and other dash cams) is to use the camera in web cam mode on your computer. You can simply move a finger back and forth until you see it enter the FOV and make note of the spot .
Click to expand...

Having not yet got around to installing my 2nd Mobius in my car (to replace the F70), I figured I'd try out the FOV.
(Got the cam out of the padded envelope & the only thing missing is the little insert for the cradle (that you screw the tripod screw into!).
Downloaded some webcam software & gave it a go.
Using a credit card held flat to the camera.
Top and bottom, it seems that maximum projection is 12mm (this is with the standard lens, card held flat to the cam body.
Didn't bother measuring the sides (because the lens is offset from the centre, there is hardly any projection available, the other side, however, should allow quite a bit.
For me, this is really good news since the camera is mounted upside-down - with the heatsink facing down, so the lens is nearest the window pillar. Good because I can shield the other side from reflections fairly well.
Obviously, if more shielding is needed on the underside (due to reflections off the dash) then the shield will need to be angled accordingly.
Using a credit card, held against the top and bottom of the lens, the furthest edge disappears at 20 degrees - so, an edge 85mm away from the lens will be just out of view. Not sure how many people would install their cam that far from their screen.
 
Have you been able to play around with your funky foam yet?
 
JakeBlade said:
Have you been able to play around with your funky foam yet?
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Yes - and it didn't work.
Well, for me.
Building a hood to shield from the sun wasn't too much of a problem but the top simply cut into the lens' view too much. I'm still finding the best angle for the cam is to have it pointing as low as possible.
To create a lower shield to try to cut out reflections was pointless. since I worked out the viewing angle was 20deg, the lower 'eyelid' (for want of a better word) simply pointed more or less straight down at the steering wheel.
It is possible that the best option (aside from the polarising filter) might be to buy an extension lens for my mobius & try to fashion an 'eyeshield (like you find on binoculars etc) out of sugru or similar (which would maybe also mount the lens on the screen)? - I think it might be a trade off - lose some of the upper and lower view (kinda like looking through a letterbox) or put up with reflections?

Just to add, I was playing with a speed display app on my mobile & noted I could see the reflected speed much of the time.
Since it's good to have a digital speed display on top of the dash (rather than a needle pointing to a vague speed on a dial amongst many hidden behind the steering wheel), I might just keep this app going.
The downside of this would be if I were to show some idiot's antics and I were speeding. The pedants out there would jump at 1 or 2mph over the limit.
 
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