Lens Closer To Windshield Better?

[Street Guardian USA]

One potential problem would be the variance in windshield angle. (how do you do a one size fits all)

 

[Dashmellow]

One potential problem would be the variance in windshield angle. (how do you do a one size fits all)

Well, that's the reason for using a bellows but it would indeed have certain limits depending on the lens used.

 

[jokiin]

I agree that I might be large but perhaps such a thing could be designed to look OK. I envision something like an elongated black wedge that could be made to look like it is supposed to be there.

the more vertical the window the easier it would be to do, of course the more vertical the window the less we actually need this

 

[Dashmellow]

It would be interesting to know the "average" rake in vehicle windscreens. Some are quite steep and other not so much but there must be a "typical" windscreen that could serve as a reference point for something like this. The lens choice would be critical but I imagine something like the 120 degrees on the SG could be used.

 

[jokiin]

It would be interesting to know the "average" rake in vehicle windscreens. Some are quite steep and other not so much but there must be a "typical" windscreen that could serve as a reference point for something like this. The lens choice would be critical but I imagine something like the 120 degrees on the SG could be used.

yeah would only work with the more narrow angle lenses or the shroud would become way too big to be practical (or acceptable at least), it's a good idea, just not sure how it could be implemented

 

[Dashmellow]

Might be worth some DIY experimentation sometime, perhaps with something like an "A" lens Mobius close to the glass surrounded by a bellows type cowling.

 

[jokiin]

Might be worth some DIY experimentation sometime, perhaps with something like an "A" lens Mobius close to the glass surrounded by a bellows type cowling.

need to put something in front of the lens on the glass, a grid pattern marked out maybe and build a reference of how large an opening needs to be created so that the filed of view isn't interrupted then once the opening is established make a shroud that is outside of that area, not easy to explain what I mean

 

[Dashmellow]

need to put something in front of the lens on the glass, a grid pattern marked out maybe and build a reference of how large an opening needs to be created so that the filed of view isn't interrupted then once the opening is established make a shroud that is outside of that area, not easy to explain what I mean

Yeah, I've done something like that before when I made a DIY lens shade for my old GT300W where the shade was made to be just shy of the camera's FOV without vignetting. Of course, in that instance the shade was to counter oblique light hitting the lens, not for windshield reflection issues.

 

[jokiin]

Yeah, I've done something like that before when I made a DIY lens shade for my old GT300W where the shade was made to be just shy of the camera's FOV without vignetting. Of course, in that instance the shade was to counter oblique light hitting the lens, not for windshield reflection issues.

ok you understood my description then, wasn't sure how well that came across

 

[Dashmellow]

ok you understood my description then, wasn't sure how well that came across

It made perfect sense to me.

 

[petepete]

just used a Mobius touching the windscreen and an adjustable shroud and the result is..

The shroud must be mat black !

following the directional line of the lens you lose the image to the point of the front of the bonnet to get rid of the reflections which could be improved by directing the shroud slightly down and it becoming more intrusive.

regarding width of the shroud, you are looking at upwards of 150mm to cover both sides.


Not a solution I would adopt or recommend ..

 

[Rajagra]

Found the thread about a 'shield' attached to the camera.
https://dashcamtalk.com/forum/threads/glare-solution.12847/
How well it might work is anybody's guess. My gut feel is to be effective it would have to be quite large and extend quite a way down and across the windshield.

Space Dude was thinking on exactly the same lines as me. i.e. addressing the actual problem - blocking the light that causes the reflection without blocking the camera's view.

I think we can agree that lens hoods will not cure the problem of reflections in one's windscreen.
Your illustrations are rather amusing as they do not represent how light and optics actually behave in the real word but I get what you are attempting to convey.

You're nitpicking. It was something I knocked up quickly to illustrate a point.
In what sense do my illustrations not illustrate how light behaves? The only thing I didn't do was spell out that the position of the reflected image was the perceived position.

Like this:

your concept of having a windscreen mounted "shield" seems quite goofy I'm sorry to say as it could never work regardless of how close you can get the lens to the windscreen. Such a "shelf" would need to be as wide as the entire dashboard and would not only block the camera's view of a good portion of the road but would likewise block the driver's view of the road as well. Your idea is just a flight of fantasy which ignores optics, physics and how a dash cam's FOV sees the road.

Well you're completely wrong there. Space Dude has proven it is feasible. In his example the shield wasn't even intrusive as it was behind the mirror and didn't cause problems. Only the tint on his screen seemed to be a deal-breaker.
Jokiin's link to the Mercedes version also proves the concept, and you have even accepted that it works.

I don't know why Space Dude didn't get more support for his idea, or why people are so resistant to it. The wide-angle issue does affect whether it is practical, but where it can be done, it will work well.

 

[Dashmellow]

Well you're completely wrong there. Space Dude has proven it is feasible. In his example the shield wasn't even intrusive as it was behind the mirror and didn't cause problems. Only the tint on his screen seemed to be a deal-breaker.
Jokiin's link to the Mercedes version also proves the concept, and you have even accepted that it works.

I don't know why Space Dude didn't get more support for his idea, or why people are so resistant to it. The wide-angle issue does affect whether it is practical, but where it can be done, it will work well.

The reason Space Dude didn't get more support for his idea is that it is highly impractical and doesn't work. While it does indeed function as a lens shade to reduce "glare" coming from below in a similar manner to the photographic barn door described above, it has no ability to eliminate reflections off the glass windshield, which is the actual issue here.

You do not seem to understand the principles involved here and your illustrations, while understandably oversimplified, provide a completely imaginary conceptualization of how your idea would function in the real world as it implies that light only travels in a single plane rather than the actual scatter patterns and reflections we are dealing with here.



You call this feasible and proven? Hah!



By the way, the Mercedes camera is a different concept completely as it is a self contained light baffle, NOT a "shelf".

 

[Rajagra]

You do not seem to understand the principles involved here

No, you don't. We aren't trying to stop glare. We are trying to eliminate the reflected image of the dashboard and objects on it.

Light travels from the object (the dash or an object on it.)
It reflects off the glass of the windshield towards the camera lens.
Putting a barrier between the object/dash, and the windshield prevents a reflection of that object being seen. It's that simple.

Why do you think the Mercedes camera is a different concept? Just because you call it a "self-contained light baffle" that doesn't change the fact that is is blocking unwanted light rays.

 

[Dashmellow]

No, you don't. We aren't trying to stop glare. We are trying to eliminate the reflected image of the dashboard and objects on it.

Light travels from the object (the dash or an object on it.)
It reflects off the glass of the windshield towards the camera lens.
Putting a barrier between the object/dash, and the windshield prevents a reflection of that object being seen. It's that simple.

Why do you think the Mercedes camera is a different concept? Just because you call it a "self-contained light baffle" that doesn't change the fact that is is blocking unwanted light rays.

I'm not interested in engaging with an entrenched bonehead any further. You should really consider reading up on optics a bit.

The Mercedes camera is an enclosed self contained light baffle that avoids reflections and scatter patterns completely because it isolates the camera from its surroundings. An open "shelf" cannot perform the same way, but based on the mythologies you are promoting here I certainly don't expect you to understand this explanation.

Edit: Just to be clear here, @Rajagra regarding my use of the word "mythologies", to quote you from your illustration....."Screen Mounted Shield: Also prevents reflection completely, but may be in an awkward place."

No, such a shield won't prevent reflections at all, much less completely. It can prevent some glare from below however.

 

[petepete]

"entrenched bonehead"


How dare you !!!!


He s British

 

[Dashmellow]

"entrenched bonehead"


How dare you !!!!


He s British

Yeah, you're certainly right about that British thing.

 

[Rajagra]

No, such a shield won't prevent reflections at all, much less completely.

Oh for the love of God. This isn't rocket science. Of course it works. I can't believe I had to go out and film a test to prove this.
Here I throw a yellow duster on to my dash. You can see the reflection in the windscreen.
I put a piece of dark card between the screen and the dash.
The reflection disappears. Oh my god what's happening??? Is this magic???

The question is not whether it will work. The question is merely whether the angle of the screen and the closeness of the lens to the screen make it practical!

 

[petepete]

Yeah, you're certainly right about that British thing.

I rest my case

 

[Dashmellow]

Try it on a sunny day, mate. This is indeed magical thinking at its worst.

Oh wait! You've made a dash mat, not a windscreen mounted "shield".