Adding a Polarizing filter to my Dash-Cam (Pics Provided)

Started 10 months ago | Discussions
Cammc
New MemberPosts: 14
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Adding a Polarizing filter to my Dash-Cam (Pics Provided)
10 months ago

Hey guys,

So I have a Blackvue DR-500GW Dashcam and during daytime I get a lot of glare and I get my dash reflected on my windshield and that shows up on my videos.

I wanted to add a polarizing filter in front of the lens in order to eliminate or reduce the problem.

So can you guys tell me what would work for me? I am still doing research into polarize filters but I thought I'd post the question now and get some input.

Do I just buy any Polarizing filter or are there different types?

One last thing is that I have found I can't add anything too far away from the lense. I would loose the viewing angle.

Time was around 19:30. It's actually worse in direct sunlight. 150X more.

This is the camera:

Camera is Blackvue DR-500GW  | 1080p HD | Lens Angle: 156°(diagonal), 123°(horizontal), 90°(vertical)

One Last thing I would like to add is that I can't add anything that is too far from the existing lens. The filter would have to sit flush with the lens otherwise I would loose the wide viewing angel.

Example: This person purchased this http://www.ebay.com/itm/Magnetic-18mm-GGS-kit-UV-filter-CPL-Polarizer-Lens-Hood-/220845646078?pt=US_Camera_Camcorder_Accessory_Bundles&hash=item336b6d20fed

Thanks

Pitbullo
Regular MemberPosts: 253
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Re: Adding a Polarizing filter to my Dash-Cam (Pics Provided)
In reply to Cammc, 10 months ago

I like the idea, but are you sure this will work properly? A polarizer works in relation to the angle of the sun. And since the car is moving, the sun will be on different angles all the time.

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Cammc
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Re: Adding a Polarizing filter to my Dash-Cam (Pics Provided)
In reply to Pitbullo, 10 months ago

Pitbullo wrote:

I like the idea, but are you sure this will work properly? A polarizer works in relation to the angle of the sun. And since the car is moving, the sun will be on different angles all the time.

See that's what I'm not sure about. That is why I came to a photography forum. I don't know how welll it is going to work.

Will it still be an improvement to add the filter? and would it affect low-light conditions? If the filter is permanently fixed to the lens, would the night time video be affected in a negative way?

Also if not the polarizing filter then what other filter will work better in this situation?

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hjulenissen
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Re: Adding a Polarizing filter to my Dash-Cam (Pics Provided)
In reply to Cammc, 10 months ago

http://www.polarization.com/water/water.html

"Can polarized sunglasses help when driving a car?

Yes. Those pesky bright reflections of the sun on the cars ahead can sometimes be attenuated a good deal. They tend to be horizontally polarized, thus perfect for vertically polarized sunglasses.  The reason is that the surfaces that you see on the car in front of you (the back window, the trunk door, and even the roof) will be slanted towards you, while the sun will be more or less aligned in the vertical plane through both cars (if not you wouldn't see its reflection from those surfaces). However, if the sun is relatively low behind you, the sun rays will be near perpendicular to the reflecting (vertical) surfaces which won't polarize the light.  The sunglasses will help more with the reflections from the glass than from the metal as the former are polarized to a higher degree.  What about the brightness of the road itself?  That light is also partially polarized, but by scattering (as opposed to reflection).  The direction of polarization will change with the direction of the road with respect to the position of the sun.  The rule is that the polarization is tangential to a circle centered on the sun.  That means that if the sun is in front, behind, or high above, the road brightness will tend to be horizontally polarized and the filter of the sunglasses will provide some help.  However, if the sun is to one side, the polarization will rotate vertically, the more so the lower the sun happens to be.  Of course, if the road is wet you get the same anti-glare power than at sea."

-h

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dsjtecserv
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Re: Adding a Polarizing filter to my Dash-Cam (Pics Provided)
In reply to Pitbullo, 10 months ago

Pitbullo wrote:

I like the idea, but are you sure this will work properly? A polarizer works in relation to the angle of the sun. And since the car is moving, the sun will be on different angles all the time.

This is a common misconception. The only circumstance in which the angle of the sun matters is with blue skies, where the effect is greatest on the part of the sky 90 degree to the sun, relative to the viewer. For other applications the ability of the polarizer to decrease glare is a function of the angle view relative to the surface of the reflecting object. The effect of a polarizer is greatest when this angle is equal to Brewster's angle, which is  a function of the refractive index of the material. If doesn't matter where the light source is -- it could be a cloudy day, without as specific location of the sun, or indoors under artificial light, with no sun at all.

Since the relationship of the dashboard camera and windshield is fixed, the effectiveness of a polarizer at reducing reflections from the windshield surface would be constant. That doesn't mean it will be good, because that would depend on the specific angles involved, but it would at least be consistent. And also, because the angles and materials causing the various reflections may be different, it may not be possible to cut all of the equally well. But just as with polarized sunglasses, there may be an angle that works well enough to cut the most bothersome reflections.

Dave

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Cammc
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Re: Adding a Polarizing filter to my Dash-Cam (Pics Provided)
In reply to dsjtecserv, 10 months ago

I really appreciate all the information guy. It's really helpful.

So you guys got anything in mind that would work for this application?

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Cammc
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Re: Adding a Polarizing filter to my Dash-Cam (Pics Provided)
In reply to Cammc, 10 months ago

Are there different kinds of polarizer filters? Is there only one spec for a polarizer filter or are there different specs for the type of filer you want?

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tko
tko
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could test the concept first
In reply to Cammc, 10 months ago

Maybe a cheap, broken or borrowed pair of polarizing sunglasses (look for clip on polarizers), taped on, just to see if it's worth buying anything better?

Otherwise you can buy polarizer filters in many different sizes. From maybe 30MM in diameter to 82MM. The smaller ones aren't too expensive, order them from any photography shop. Use clay or tape to hold it on and experiment with the best rotation (has to to be put on at the right angle to do the best job.) You could then just use silicon rubber to hold the film on, or come up with some type of a semi-permanent mount.

Here's an example of low cost but decent polarizer that might work. Circular or linear doesn't matter. Multicoating probably doesn't matter too much for you. Name brands might work better.

http://www.adorama.com/HY55PL.html

Funny thing is, smaller filter costs more.

http://www.adorama.com/TF25CPL.html

http://www.adorama.com/VVCPL49.html

You could try ebay, look for a bargain or broken one.

This film is cheap enough to play with. Cut and glue around edges.

http://www.amazon.com/Polarizing-Filter-2-75/dp/B009P8B4S0/ref=sr_1_2?s=industrial&ie=UTF8&qid=1370379930&sr=1-2&keywords=polarizing+film

Cheap clip ons. Maybe cut to fit?

http://www.amazon.com/Polarized-clip--flip-up-plastic-sunglasses/dp/B000HJKGMG/ref=sr_1_1?s=apparel&ie=UTF8&qid=1370380066&sr=1-1&keywords=polarizing+clip+on

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FrankieJ
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Re: Adding a Polarizing filter to my Dash-Cam (Pics Provided)
In reply to Cammc, 10 months ago

I'd consider taking a different approach. If the problem is glare from the dashboard reflected in the windshield - decrease the reflectance of the dashboard.
I shoot from my car also and have found that using a dark and textured dash board cover eliminates 90%+ of the problem. My dash board cover is made from a black short-pile carpet type material and works great for eliminating glare, for photography AND regular everyday driving. Not a pitch for any brand but I believe mine is a Dash Topper. they're all custom fit per vehicle and work great.

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