"Poor Man's" Polarizer for SG9665xx, A118xx, and B40xx

DT MI

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#1
Inspired by Niko's DIY polarizer for the SG9665GC and the discussion that followed in this thread - https://dashcamtalk.com/forum/threads/magnetic-cpl-lens-filter-for-street-guardian-sg9665gc.10942/ - I decided to try doing something with items I had laying around the house and that would work for both my SG9665GC and A118-C. More importantly it had to be cheap and easy.

Being as how my favorite non-permanent fastener is Velcro tape I wanted to use it, especially since I have a lot of it around.

Next was the polarizer itself - not something most people have laying around (I do but all my 35mm lens filters are much too large and much too expensive to donate to this project). In a flash of 'genius' (stimulated no doubt by my going outside and putting my sunglasses on) I decided to sacrifice a pair of clip-on sunglasses, a relatively cheap solution if you don't already have a pair laying around and need to go buy one. I figured if it worked as eyeware it should work on the dash cam as well.

Here's the sunglasses I used - after hacking it up.

01-ClipOnSunglasses.JPG

Cut the lens to roughly the shape of the lens housing - a decent pair of household scissors is more than adequate for the job. I wasn't sure if top/bottom orientation made a difference so I cut it straight on the top and with a bit of a curve on the bottom so I could mount it on the camera the same way they would be on my eyeglasses. Affix Velcro along the sides in the rear -

02-03-Filter.jpg

Next I cut some (very) small pieces of the matching Velcro to attach the lens to the camera, ...and put them on the camera.

04-05-Velcro.jpg

It's then just a matter of sticking the polarizer on the camera.

06-07-OnCamera.jpg

I had initially used a strip of industrial strength Velcro along the edge but it was too thick and caused vignetting so I took it off and replaced it with the small pieces of household Velcro and that took care of the issue.

08-Vignette.jpg

Now, after all this the big question - Does It Work?

Yes, but not without some issues.

A118-C (rear camera) without (top) and with (bottom)-

10-A118-C.jpg

It does a pretty good job of removing reflections in the center of the glass but not so much at the bottom. I have the A118-C installed as a rear cam and with the slope of the window it's positioned so that the sun hits it pretty much all the time. The vehicle has a light colored interior and cargo cover so reflections were quite bad because of that.

Also notice that the polarizer was a bit dusty and had some spots on it that really show up when the sun hit the lens directly. It will be necessary to keep it pretty clean. Also, having the sun hit it directly causes a 'sun spot' to show up in the video - the only solution to this is to not drive in the sun but then reflections wouldn't be an issue either.

SG9665GC without (top) and with (bottom) -

11-SG9665GC.jpg

I don't have the 'GC' mounted on the windshield (windscreen), it's on the underside of the rain sensor housing, so it's a bit protected from direct sunlight so in this example no dust is showing.

One of the concerns I had is how this would affect night performance of the cameras since the sunglass lens material is pretty dark. I haven't had an opportunity to drive after dark yet but we do have some very long lighted underpasses that might substitute.

SG9665GC functioned pretty well -

12a-SG9665GC-Noise.jpg

A118-C not so well (keep in mind that the rear of my vehicle has some pretty dark privacy glass so this is NOT an accurate side-by-side comparison - it may perform better in front)

12b-A118C-Noise.jpg

Finally here's a video clip driving through the underpasses - SG9665GC followed by A118-C. It's pretty obvious that A118-C really struggled with the combination of dark environment, dark filter and dark privacy glass.


Edit: Just for a point of comparison I put an SG9665GC with the filter in the rear to see how is would handle the dark glass and a filter. Here's the video.


It's obvious that it works much better than the A118-C.

Conclusion -

It's a cheap (no cost to me since I had everything on hand - $10 for enough material to do at least 4 cameras if you had to buy everything) and easy (I could do a camera in 10 minutes or less now that I've got it figured out) solution.

I've decided to not use it on the A118-c rear cam, at least for the time being, because the benefit doesn't outweigh the downside I expect with night time performance. I'll keep it on the 'GC' at least until I test it in actual night driving conditions and see how it works out then.

Even if it turns out that night performance is unacceptable it's easy enough to just pull the filter off the camera and put it back on the next morning. Another piece of Velcro on the side of the camera could be used to store the filter and keep it from getting lost when not in use.

The A118-C would probably do better in low-light as a front camera vs. in the rear with privacy glass.

Performance would be better with both cameras if I could find a pair of sunglasses with lighter lenses than the ones I used.
 
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Street Guardian USA

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#2
I'm not sure sunglasses use a Circular polarizing filter I think it's Linear? (not sure) It might partially work, but don't think it will get the results you want.
 
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DT MI

DT MI

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#3
I'm not sure sunglasses use a Circular polarizing filter I think it's Linear? (not sure) It might partially work, but don't think it will get the results you want.
It is a linear polarizer. CPL's are necessary for the auto-focus/auto-exposure to work properly in an SLR camera where those systems won't function properly with a linear. I'm sure better lens material will result in better performance - but as the title says it's a "Poor Man's" solution. :D

Edit: I'm actually quite pleased with the reduction in reflection obtained. The sample I posted of the 'GC' is pretty typical. There will always be conditions where performance is better or worse.
 
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Sunny

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#4
I need one for the Rexing V1.
Dash reflection is terrible.
 

Dashmellow

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#5
Some people have reported good results from using circular polarized lenses from 3D movie glasses to make "poor man's dash cam polarizers" such as those used in RealD 3D cinema.
 
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DT MI

DT MI

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#6
Some people have reported good results from using circular polarized lenses from 3D movie glasses to make "poor man's dash cam polarizers" such as those used in RealD 3D cinema.
Actually I have a pair of these around here somewhere. I just wanted , at least to start, the cheapest solution.
 

Dashmellow

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#8
Actually I have a pair of these around here somewhere. I just wanted , at least to start, the cheapest solution.
3D movies glasses are pretty cheap. :), probably even cheaper than those clip-0ns. WAIT! Those clip-ons look just like the ones I'm missing. Where did you get those?! :p
 

Sunny

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#9
3D movies glasses are pretty cheap. :), probably even cheaper than those clip-0ns. WAIT! Those clip-ons look just like the ones I'm missing. Where did you get those?! :p
I have bunch of those somewhere from the last movie.
 

Bungus

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#10
I did similar cheap way using a standard bottled water cap, unused old clip on sunglass(brown), grazy glue for my Mobius A.
Work great in daytime. Horrible at night.
 
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DT MI

DT MI

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#11
Edited my original post to include a video of the SG9665GC with filter mounted in the rear of the vehicle where the dark privacy glass pretty much caused the A118-C to go belly up.

Edit: Here's the added video -


Edit 2: Here's a picture showing how dark the privacy glass is - a piece of white paper taped to the inside and outside of the rear glass.

DarkGlassSmall.jpg
 
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jokiin

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#12
Edited my original post to include a video of the SG9665GC with filter mounted in the rear of the vehicle where the dark privacy glass pretty much caused the A118-C to go belly up.

Edit: Here's the added video -

that with the filter and through privacy glass?
 
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DT MI

DT MI

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#13
that with the filter and through privacy glass?
Yes (I should have been a little more careful about alignment). I'm quite impressed with the 'GC' under those circumstances, especially after seeing how the A118-C pretty much fell on it's face under the same conditions.

Tomorrow I should have the opportunity to use them (1 front, 1 rear with privacy glass) after dark with the filters. I'm looking forward to seeing those results.
 

jokiin

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#14
Yes (I should have been a little more careful about alignment). I'm quite impressed with the 'GC' under those circumstances, especially after seeing how the A118-C pretty much fell on it's face under the same conditions.

Tomorrow I should have the opportunity to use them (1 front, 1 rear with privacy glass) after dark with the filters. I'm looking forward to seeing those results.
I would reasonably expect the night results to not be as good, I'm surprised how well it is working during the day though
 
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DT MI

DT MI

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#15
I would reasonably expect the night results to not be as good, I'm surprised how well it is working during the day though
You'll probably be quite pleased with how well it works at night (at least as a front camera). Not as good as without the filter but still usable.

Relatively dark street with polarizer filter -


...and same street without the filter -


Unfortunately it doesn't do as well as a rear camera with dark privacy glass and the filter (same street) -


...and without the filter (again, same street) -


For comparison here's the A118-C as a rear camera without a filter (once again, same street) -


My opinion at this point is a polarizer is a viable option on a front camera (especially if I can find a lighter grey to use) if you're willing to sacrifice a bit of night quality. As a rear camera in a vehicle with privacy glass it looks like a polarizer will only be usable as a daylight option.
 
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DT MI

DT MI

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#17
I just added a picture to post #11 in this thread to show how dark the privacy glass is in the rear hatch. Makes the performance of the SG9665GC even more impressive.
 

gabi_o

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#19
Hello!
Did someone tried to cut a piece of filter DSLR? It's pretty cheap and worth trying.
Ex: here or here
I have a A118C.
 
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DT MI

DT MI

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#20
Hello!
Did someone tried to cut a piece of filter DSLR? It's pretty cheap and worth trying.
Ex: here or here
I have a A118C.
The biggest problem would likely be trying to get a good cut on the glass - the lenses I used were soft plastic and easy to work with. Other than that it should work as well as anything else.