Remove Reflection with lens hood?

[Dashmellow]

The lens hood in question as presented by the OP is essentially a different concept as compared to the Performance Data Recorder which is not optimized as a general purpose dash cam.

For one thing, it is angled quite high with far too much sky for typical dash cam usage. BTW, the previous examples above are all from the first 2015 iteration of Corvette's Performance Data Recorder. The more recent iteration below seems to have eliminated the vignetting and reflections of the earlier version.



One way or another, a lens hood is not a practical approach to eliminating windshield reflections, although I maintain that it could be made to work assuming one could tolerate the size of the thing.

 

[TonyM]

Even if we limit the FOV to your red box, the bottom of the lens hood would still need to go down to the bottom of the glass and block the driver's view completely.

My example is from a SG9665GC which is mounted a few cm from the windscreen. Move the lens to the glass, and the hood size reduces.

I agree with @Dashmellow that it is generally impractical but can be made to work, if we are willing to accept the hood itself being within the 16:9 frame - or go for the 32:9 video you have mentioned in the past to crop out the hood.

 

[Nigel]

or go for the 32:9 video you have mentioned in the past to crop out the hood.

That would help, but most people are going to want the front of their bonnet in the FOV so that there is some reference point that allows distance to be judged, so you are not going to move the bottom of your red box up by much.

 

[Nigel]

BTW, the previous examples above are all from the first 2015 iteration of Corvette's Performance Data Recorder. The more recent iteration below seems to have eliminated the vignetting and reflections of the earlier version.

And the thread that goes with it, complaining of other issues: https://www.camaro6.com/forums/showthread.php?t=543783

5.3 Mb/s bitrate!

 

[Dashmellow]

And the thread that goes with it, complaining of other issues: https://www.camaro6.com/forums/showthread.php?t=543783

5.3 Mb/s bitrate!

Who the F cares? The Corvette PDR is NOT a traditional "dash cam" as we here on DCT might define one as it was designed with a different primary purpose in mind. And the camera's bit rate or resolution has nothing whatsoever to do with this discussion, but of course, it seems you feel compelled to find "something" to attack.

 

[EGS]

It is funny that the person who started the tread didn't go beyond his first one, so evidently he quickly figured out his own answer. yet you guys are slapping at each other... for what gain?

 

[Dashmellow]

It is funny that the person who started the tread didn't go beyond his first one, so evidently he quickly figured out his own answer. yet you guys are slapping at each other... for what gain?

I dunno, ask Nigel, he's the one who always instigates these sort of spats.

 

[EGS]

beginning to see the pattern, but one must be smart to pull away from a toxic environment.

 

[Matt_V939]

It is funny that the person who started the tread didn't go beyond his first one, so evidently he quickly figured out his own answer. yet you guys are slapping at each other... for what gain?

Oh, come on' not just sitting here eating popcorn (which I don not like, by the way), I'd chime in if i had something more to say.
And sometimes interesting points come out from OT comments.
All consideration are interesting; and among solutions to avoid reflection a small crop might be a better compromise compared to the loss due to a filter.

 

[TonyM]

I've taken some measurements and drawn a sketch of how large a lens hood I would need in my car, if I install a Mobius tight against the windscreen, and keep just the very front of the car visible.

The lens hood would be angled at just 16deg down from horizontal. and would extend about 180mm in front of the camera, which as we have discussed earlier, is not really practical. I would much rather fit a polariser.

 

[Nigel]

So you would effectively have a vertical field of view of 16 x 2 = 32 degrees?
What aspect ratio does that give?

 

[TonyM]

I was thinking of a typical 130deg FOV camera, and the lens hood cropping out the bottom 1/3, as mentioned previously.
So that changes the aspect ratio from 16:9 to 16:6

 

[Nigel]

I assume that although that is possible with the Mobius, it does rely on the camera being mounted at the very top of the glass, where an A129 couldn't go and is not covered by the wipers anyway?

From the position of the camera in your red box image, it is clear that green line on your diagram runs through the glass much lower down, near the bottom of the glass rather than 3/4 way up.

 

[TonyM]

I used the highest practical mounting position on the glass - at the underside of the dotted area around my windscreen and still within the swept path of the wipers.

 

[jokiin]

It's actually quite similar to what @jokiin mentioned in regard to the way shrouds on factory fitted cameras function.

these are the types of things I was referring to, as used for ADAS systems, these are also DVR's, not quite dinner plate size

 

[Harsh]

I doubt such models have a FOV equal to or wider than the Mobius A2.

 

[jokiin]

I doubt such models have a FOV equal to or wider than the Mobius A2.

I'm sure they don't, subject was only about what may or may not be possible though, what's possible isn't always practical

 

[Dashmellow]

these are the types of things I was referring to, as used for ADAS systems, these are also DVR's, not quite dinner plate size

View attachment 48610



View attachment 48611

Yes, that is quite similar to the photo of the one on the Corvette I posted back in post #14. I agree with Harsh that the FOV wouldn't be the same as a typical dash cam but if the shroud design was carefully matched with the lens I suppose it could probably offer decent coverage.

As for the "dinner plate" size (10" in diameter) I wasn't all that far off. I didn't have much time today but I did a quick, rough experiment with a sheet of black foam core and held it at an angle against the dash cam on my front windshield. I was able to shroud the bottom of the camera to include the view of the dashboard without interference. I learned that a shroud could be fabricated that would work but it would need to be approximately 15 inches tall and about that wide to accommodate the FOV of the lens. So, as I said earlier in the thread, the concept will work but the shroud would have to be impracticality large.

 

[SawMaster]

To add another 'variable' the 'shroud' could be made from slats, allowing driver visibility but not mitigating the appearance problem or the lack of stealth this approach seems to have as an inherent unwanted quality.

In my business I'm often heard telling people that just because something can be done is usually not reason enough to do it

Phil

 

[Nigel]

The purpose of the shroud is not to prevent reflections getting to the camera, it is to prevent reflections reflecting off the glass, thus every part of the glass that can be seen by the camera needs to be inside the shroud and the shroud needs to have a non-reflective surface so that the shroud can't be seen, or at least have an evenly reflective surface.

I was able to shroud the bottom of the camera to include the view of the dashboard without interference.

If the camera can see down to the dashboard without interference from the shroud then all of the glass needs to be inside the shroud? Otherwise the part of the glass outside the shroud will have reflections on it.

To add another 'variable' the 'shroud' could be made from slats

Good solution, but you would inevitably see strong reflections of the slats in the image...