Remove Reflection with lens hood?

[Matt_V939]

Will this work???

Remove Reflections with These Rubber Smartphone Lens Hoods

Ultimate Lens Hood is back with an affordable option for smartphone filmmakers.

nofilmschool.com

 

[jokiin]

Will this work???

it would, same reason you see black shrouds around factory fitted cameras for things like lane departure systems etc

 

[Nigel]

Not with a dashcam, only with a very narrow angle lens, even a smartphone may require zooming in to avoid the hood being visible.

 

[jokiin]

this particular device is not a practical solution for our application, the science behind it stacks up though

 

[SawMaster]

I remember an Akenori brand dashcam which had a built-in hood, but it wasn't around for long. Don't know of any other dashcams which have hoods, but it would be easy enough to DIY something.

Phil

 

[Dashmellow]

This idea comes up here on DCT now and again. The concept is basically sound, except that due to the FOV of virtually all typical dash cams you'd need a rubber lens hood the size of a dinner plate for it to work.

 

[Nigel]

This idea comes up here on DCT now and again. The concept is basically sound, except that due to the FOV of virtually all typical dash cams you'd need a rubber lens hood the size of a dinner plate for it to work.

I think that would be a feast fit for a king!

Remember that some dashcams can see the bottom of both A-pillars, and most are close to that, and almost all can see down to the dash, thus the hood would need to reach beyond that to stay out of sight.

 

[TonyM]

I remember an Akenori brand dashcam which had a built-in hood, but it wasn't around for long. Don't know of any other dashcams which have hoods, but it would be easy enough to DIY something.

Phil

In principle, it worked. In practice, the field of view was too small to be useful.

I tried to find out what happened to the project but never heard anything.

 

[Dashmellow]

I think that would be a feast fit for a king!

Remember that some dashcams can see the bottom of both A-pillars, and most are close to that, and almost all can see down to the dash, thus the hood would need to reach beyond that to stay out of sight.

Ultimately it depends on the FOV angle along with how far the lens is positioned from the glass but one way or another it would need to be quite large.

The last time this discussion came up I suggested that a large format view camera bellows type lens hood might work and such a device could be positioned against the angle of the glass fairly easily. As long as the hood will encompass the cone of lens coverage it would work. One can get a rough approximation of the edge of the cone of coverage just by moving your hand in and out of the FOV near the camera.

 

[Nigel]

One can get a rough approximation of the edge of the cone of coverage just by moving your hand in and out of the FOV near the camera.

Yes, if I put my hand on the dash close to the glass then my dashcam can see my hand, thus the hood would need to be so big that the driver would not be able to see anything! It is not a practical solution.

Only solution I have seen for totally removing reflections is this:

 

[Dashmellow]

Yes, if I put my hand on the dash close to the glass then my dashcam can see my hand, thus the hood would need to be so big that the driver would not be able to see anything! It is not a practical solution.

Only solution I have seen for totally removing reflections is this:

You sound clueless.

 

[Nigel]

You sound clueless.

I'll believe it is practical for a car dashcam when you post some images to prove it is practical

Of course it can be done on a bus, or other vehicle with a vertical screen, since then you can get the lens close enough to make the hood a practical size.

 

[Dashmellow]

I'll believe it is practical for a car dashcam when you post some images to prove it is practical

Of course it can be done on a bus, or other vehicle with a vertical screen, since then you can get the lens close enough to make the hood a practical size.

it would, same reason you see black shrouds around factory fitted cameras for things like lane departure systems etc

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

Personally, I don't advocate or have any interest in using a lens hood on a dash cam to eliminate reflections but indeed a big enough shrouded hood would do the trick as long as it could encompass the FOV close enough to the camera that it can seat against the glass without interfering with the lens coverage.

I'm not interested in posting any images to prove anything here Nigel, there is no need too. But yet once again, your goal seems to be to initiate some sort of pissing match with me, as it is with literally every interaction you initiate with me.

Piss off.......

 

[Dashmellow]

BTW, since 2015 the Chevrolet Corvette features what they call the "Performance Data Recorder" , aka - dash cam.

It is a camera at the top of the windshield inside a "shroud", aka- lens hood.

The PDR, aside from the various unique performance functions provides a view of the road which includes a view of the car's hood.

A leap to a wider lens, closer to the glass with a larger shrouded lens hood is more than doable.

Fancy that!

 

[jokiin]

the question was will it work, of course it can work, is it practical for our specific application, not in most cases, that doesn't mean it doesn't work though

 

[Nigel]

Fancy that!

Check out some videos from that camera ... at times there are some strong dash reflections visible, obviously doesn't even have a CPL, certainly not a full shroud!

 

[TonyM]

When I tested the Akenori NX01 it had one major problem - it only worked on steep sloping windows. The lens vertical adjustment did not go far enough to bring the horizon anywhere near to 50:50 on the video.

I modified the shroud by adding a few layers of VHB to the front edge, which tipped the camera down far enough to make it useful. In testing alongside a Mobius 1 and a GC, you can see the NX01 had such a small FOV that not even the front of the car is visible. However, it does prove that the shroud is a feasible solution to eliminate dashboard reflections.

 

[Dashmellow]

Check out some videos from that camera ... at times there are some strong dash reflections visible, obviously doesn't even have a CPL, certainly not a full shroud!

Still missing the point Nigel, as usual. But that's your style of argument, apparently.

Back to the original statement, a flexible lens hood on a dash cam would need to be quite large to avoid vignetting (probably impractically so) but it hardly would need to "reach beyond (the A pillars) "to stay out of sight." It only needs stay out of the way of the camera's FOV angle and have the ability to meet the glass.

 

[TonyM]

Our current 16:9 cameras can see inside the windscreen all the way down to the dashboard, and often outwards to the bottom of the A-pillars.

If we can live with the bottom edge of the video being somewhere around the front edge of the car, then the lens hood can be limited in depth, occupying the lower 1/4 of the frame.


The hood size can also be minimised by bringing the lens as close as possible to the window.

Akenori told me that my windscreen angle is 23 degrees, apparently much shallower than many popular cars? I have not verified this or compared to other cars, but obviously the shallower the windscreen, the larger the hood needs to be.

 

[Nigel]

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.

Which is why Chevrolet didn't put a bottom surface on the hood of their "Performance Data Recorder" even though it is of narrower FOV than any of our dashcams, and why it does have dash reflections: