My DIY $6.45 CPL filer for my A119

[DavidUK]

Here's a thing though... many here speak of the difficulty of getting the right orientation of the CPL so as to cut out most reflections from the dash.
"It's difficult to turn when fitted" or "I have to keep taking it off to revolve it" etc.
But, why not just hold the CPL up to your eye and look out of the windscreen while revolving it, like I did with my mobile phone glass?
Does the A119 have something that would give it a different view when the CPL is attached, or is my eye going to see exactly the same reflections with/without the CPL as the A119 does?
Might save some setting up hassle!

 

[DT MI]

...But, why not just hold the CPL up to your eye and look out of the windscreen while revolving it, like I did with my mobile phone glass?
Does the A119 have something that would give it a different view when the CPL is attached, or is my eye going to see exactly the same reflections with/without the CPL as the A119 does?...

The polarization (and resultant reflection reduction) occurs within the filter so the image that reaches your eye should be the same as that reaching the camera lens.

About the only thing that could be happening in the A119 that would have an effect would be if it had an internal polarizing filter between the lens and sensor, but if that were the case then an external one would be unnecessary.

 

[DavidUK]

Thanks @DT MI - as I have it here I'll carry on with my experiment of how to mount it. May not have time until the weekend, but I have a few ideas.

Unfortunately, I dropped the linear filter and don't know which was around it should be! Any way of finding out, or doesn't it matter with linear?

 

[DT MI]

Unfortunately, I dropped the linear filter and don't know which was around it should be! Any way of finding out, or doesn't it matter with linear?

I don't think it will matter, but again it would be easy enough to verify by just looking through it and evaluating the reflection reduction from each direction.

 

[DavidUK]

Yes, the whole thing is trial and error!

The simplest solution, once I have the correct side and rotation, will be to stick the thin polarising film, 16mm diameter, in the centre of one of my M14 self adhesive rubber washers, 19mm outer/14mm inner diameter, using 1mm of the washer's internal adhesive radius. Then, with the remaining 1.5mm outer adhesive radius, and having previously cut off a flat at the top and bottom of the washer, stick the washer and filter to the front of the 16mm x 16mm lens housing. The 1.5mm thick washer does not cause vignetting on its own and so the addition of the very thin polarising filter should maintain this.

Not too keen on the plastic filter as it's thin, fiddly, and will scratch more easily when I try to clean my fingerprints off it many, many, times!

...yes, I know... take some photos!!

 

[DavidUK]

Well, I've tried sitting in the car with the linear polariser up to my eye and... yes, it does get rid of the reflections. Doesn't seem to matter which side I look through. So, spurred on, I find myself modifying...

...the phone clamp... ...and also using the black inner lens locking ring... ...

I found the locking lens ring fits the thread in the clamp, so I took hacksaw, craft knife, sand and emery paper to the clamp...

Then I sanded down the thickness of the "new" filter housing so three's no vignetting when held in front of the A119's lens. And so I'm left with...



The outer ring will be clear glued to the A119 lens housing, the filter inserted at the correct rotation and the inner ring secures. I'm conscious the filter may rotate when the locking ring is screwed in, but I have ideas how to prevent that. Will finish and fit at the weekend.

 

[Nigel]

Well, I've tried sitting in the car with the linear polariser up to my eye and... yes, it does get rid of the reflections. Doesn't seem to matter which side I look through. So, spurred on, I find myself modifying...

It is only circular polarising filters that need to be the correct way around, if the light goes through the quarter wave plate first then it is no longer horizontally polarized when it reaches the linear polariser.

The light from the reflections will be mainly horizontally polarised, so you want your linear polarizer exactly vertical to cut out the reflections. You can test the position by holding it up to a TV screen, most TV's (except 3D ones) are vertically polarised so that you can see them through polarized glasses, if you hold the filter at exactly 90 degrees to what you want it in the car then it should completely cut out the TV image. Most LCDs used in cars are diagonally polarised as the designers didn't know which way up they would be mounted and diagonally means that they can be viewed through polarized glasses whichever way up they are, although only at half brightness! So if you test it against a car LCD it should cut out the image at 45 degrees to how you want it mounted. If you want to test your TV, use some polarized sunglasses, they are vertically polarized like you want your filter to be.

 

[RCPilot]

Glad you may find some of my DIY CPL ideas to be used on A119. After you finish your project you may share results here or in DIY section.

The GGS filter arrived today. Seems good quality. There is a thin metal washer with an adhesive on one side to stick it to a camera lens. Given the surface area to mount it on the A119 is limited, I don't think the adhesive will hold, specially in the heat. I used a tiny dab of epoxy on two edges to make sure it would not come off and get lost of damaged. The lens is about 5.7mm thick and has 3 magnets to hold the lens to the metal ring. The lens can still move about 10 degrees laterally with the lens installed.

There is some vignette when using this filter . I did not see an easy way to remove the lens to make the lens holder thinner. I carefully sanded it down to 5.1mm but it didn't change the amount of vignette to a significant degree, so I don't recommend reducing the thickness of the holder as it's not worth the hassle for minimal reduction. However, I don't think the amount of vignette will be of any concern, unless you are a OCD person. You may be able to see in the picture of the mounting ring that it is not centered on my lens. That was intention as that was the position that gave me the least amount of vignette. I was still a little off but close enough. Not going to be filming anything super special to worry too much about the corners, specially with such a wide angle lens.

Tomorrow I'll shoot and post some video. I think this should work fine as a permanent CPL filter for my A119. If I get some spare time, and motivation, I may pull the lens out and mount a ring around the lens like @niko did to make it low profile and eliminate the vignette. I was hoping the GGS holder was going to be thin enough to not have any vignette but it wasn't.

@DavidUK - I looked at the GGS though a mirror and light goes though the same on either side, so I guess it is a linear polarizing filter? Testing it in the house it seemed quite effective in reducing reflected light.

 

[DavidUK]

@RCPilot - could you tell me what diameter and thickness the bare lens is when you have it out of its holder? Thanks.

 

[Nigel]

@DavidUK - I looked at the GGS though a mirror and light goes though the same on either side, so I guess it is a linear polarizing filter? Testing it in the house it seemed quite effective in reducing reflected light.

You probably worded that wrong.

For those that don't know, the test to distinguish a CPL from a linear polarizer is to look through the CPL at your eye reflected in a mirror. If it is a CPL then you will only be able to see your eye if it is the correct way around for the camera to look through it, if it is a linear polarizer then you will see your eye whichever way around it is.

 

[RCPilot]

I'm not that happy with the filter. When there is direct light coming in it is causing a lot of reflections and distortion. I didn't notice that happening with the flimsy plastic filter. Maybe because the plastic filter was closer to the cam's lens? I would not think a small difference in distance would account for all of that. When there is not direct light into the filter it works fine. Next step is to pull it out of the housing and attach it directly to the camera with some double sided tape. My dash BTW is pretty bad when it comes to reflecting a lot of light onto my windshield. I'll post lens diameter and thickness when I get around to pulling it out of holder...

 

[RCPilot]

Ok, I think I figured out the issue. The metallic ring that sticks onto the camera is very reflective, I think it is the cause of all the reflections and distortion. Off it goes soon... Or maybe I will black it out.

 

[RCPilot]

Ok, OCD kicking in. The lens is glued in the holder. I cut it out. Lens is 1 mm x 20.75 mm. @DavidUK

 

[RCPilot]

I attached just the lens using the same setup @niko devised. (Metallic ring around lens edge setup with magnets on cam.) Works much better. In the one pic below into direct sun you can still see some dash reflections, but it's about 75% less than without it. Going to leave it alone for a while now.

Note that the GGS lens scratches very easily. After cleaning it a few times from all the handling from remounting it, I noticed a lot of small fine scratches.

 

[Gibson99]

I'm not that happy with the filter. When there is direct light coming in it is causing a lot of reflections and distortion. I didn't notice that happening with the flimsy plastic filter. Maybe because the plastic filter was closer to the cam's lens? I would not think a small difference in distance would account for all of that. When there is not direct light into the filter it works fine. Next step is to pull it out of the housing and attach it directly to the camera with some double sided tape. My dash BTW is pretty bad when it comes to reflecting a lot of light onto my windshield. I'll post lens diameter and thickness when I get around to pulling it out of holder...

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You can cut a lot of that glare and overexposure by aiming your lens down a lot. Most people suggest you should have the horizon be just above the center of the frame. yes that means your dash/hood will now be visible, but that's not so bad. It will give a better idea of where cars are when they're right alongside you, which can be extremely useful in the case of a lane change accident, especially since this will let you see Kane nations better too.

 

[RCPilot]

Good suggestion, I'll give it a try. The reason I pointed it as I did was to keep my hood out of the frame as I thought all that white space reflecting into the camera would result in underexposed video. (But in the most recent video most of my hood is in the frame.) BTW, what is "Kane nations"?

 

[Gibson99]

Good suggestion, I'll give it a try. The reason I pointed it as I did was to keep my hood out of the frame as I thought all that white space reflecting into the camera would result in underexposed video. (But in the most recent video most of my hood is in the frame.) BTW, what is "Kane nations"?

Most dashcams ignore the bottom half of the video frame when determining metering because the hood is never a good reference point, as it could be so many different colors.

Kane nations is an autocorrect fail plus lack of proof reading. Should have been "lane markings"

 

[DavidUK]

I was just thinking... my son is an Optometrist. His optician shop cuts down lenses every day. Why don't I buy a glass PL or CPL camera filter for a few quid and have him cut it to size? Hey, I wonder if he can cut to a 17mm x 16mm rectangle with rounded corners!

I think PL would be better as a CPL may delaminate when the edge is being cut (ground) away.

I'll ask him tonight...

 

[Sutton]

I was just thinking... my son is an Optometrist. His optician shop cuts down lenses every day. Why don't I buy a glass PL or CPL camera filter for a few quid and have him cut it to size? Hey, I wonder if he can cut to a 17mm x 16mm rectangle with rounded corners!

I think PL would be better as a CPL may delaminate when the edge is being cut (ground) away.

I'll ask him tonight...

Dave regarding the A119 do you think buying the CPL when it is released a good idea, will it really cut down the glare What percentage of reduction would it approx. cut down?

 

[RCPilot]

Forgot to post pics of latest CPL. I need some smaller magnets...