CPL Filter Help

[ljw2k]

I have a Viofo A119S and I have purchased a genuine Viofo CPL Filter but need help setting it up please. I have followed the instructions made here

but can't get my head around why I need to set it to 45*

I have made a small video clip and just need to confirm when I tilt the camera 45 degree the screen goes black on my TV/Monitor.

I would have thought when the camera is straight the screen goes black to cut out unwanted light?

 

[jokiin]

they are preset, nothing you need to change

 

[ljw2k]

Mine wasn't pre-set it was miles out until I set it to the youtube video, I did this by turning the round glass filter so the screen went black as per the video @ 45 degree's

 

[jokiin]

45 degrees is only appropriate if the LCD you are testing it against is polarised at 45 degrees, many are at 90 degrees, being miles out doesn't sound right

 

[DT MI]

As @jokiin said, using any LCD screen as a tool the results could be affected by how the screen itself is polarized - all LCD screens are polarized and there is no standard. The only way to determine if a given CPL is aligned correctly is by checking actual reflections in the vehicle - this eliminates any outside variables such as the characteristics of a specific LCD screen. See this post: https://dashcamtalk.com/forum/threa...nt-how-to-adjust-diy.15022/page-2#post-197505

 

[ljw2k]

Thanks for the replies and I will adjust the CPL while in the car, not the easiest of filters to adjust while on the camera.

 

[DT MI]

Thanks for the replies and I will adjust the CPL while in the car, not the easiest of filters to adjust while on the camera.

No need to do it on the camera. Just look through the filter directly while holding it and rotate until you get to the point where reflections have the maximum reduction. You now know the proper orientation and can proceed accordingly.

 

[Harsh]

I've had to readjust both my CPL's more than once. VIOFO needs to put a dab of glue (like on the SGGCCPL) to hold the filter in place.

 

[jokiin]

I've had to readjust both my CPL's more than once. VIOFO needs to put a dab of glue (like on the SGGCCPL) to hold the filter in place.

the very first batch weren't aligned correctly, this was rectified long ago

 

[Harsh]

I've had to readjust both my CPL's more than once. VIOFO needs to put a dab of glue (like on the SGGCCPL) to hold the filter in place.

the very first batch weren't aligned correctly, this was rectified long ago

CPL bought for the A119 was also a little off. The glass tends to dislodge from the grooves and gets misaligned.

 

[Harsh]

 

[Street Guardian USA]

A TV that's polarized at 90 is the easiest.

 

[ljw2k]

I adjusted mine while in the car holding the filter until the glare disappeared, I put a white piece of paper on my dash to help me .

 

[DT MI]

A TV that's polarized at 90 is the easiest.

But what's not easy is determining how your TV is polarized. Absolutely nothing else needed to do the check in the vehicle with the actual reflections that are being reduced.

 

[Nigel]

But what's not easy is determining how your TV is polarized. Absolutely nothing else needed to do the check in the vehicle with the actual reflections that are being reduced.

TVs are always vertically polarised, otherwise people with polarised glasses wouldn't be able to watch TV and there would be a lot of complaints!
(Except the 3D circularly polarised ones)

If you want to check your TV, use some polarised glasses like in the above pictures, the CPL ought to be orientated in the same way as the glasses because it has the same job to do.

 

[DT MI]

TVs are always vertically polarised, otherwise people with polarised glasses wouldn't be able to watch TV and there would be a lot of complaints!
(Except the 3D circularly polarised ones...

Therefore all TVs are not vertically polarized.

...If you want to check your TV, use some polarised glasses like in the above pictures, the CPL ought to be orientated in the same way as the glasses because it has the same job to do.

I don't need to check my TV - I align my CPLs by directly observing a reflection, which is the way it will be used in real life.

 

[Street Guardian USA]

My Samsung TV and PC Acer monitor are both 90 so it’s very convenient for me to double check CPL’s are calibrated properly.

 

[Nigel]

Therefore all TVs are not vertically polarized.

True, CRT TV's aren't either, but like 3D TV's they are museum pieces and almost impossible to buy these days.

 

[nutsey]

True, CRT TV's aren't either

As well as back projection TVs and PDPs (plasma display panels).

 

[DT MI]

My Samsung TV and PC Acer monitor are both 90 so it’s very convenient for me to double check CPL’s are calibrated properly.

And that's very convenient for you since you know that for a fact - and - you probably check scores, or even hundreds, of CPL regularly.

However, if I were a manufacturer/vendor/consultant I would NOT tell a customer to use a specific methodology unless I was absolutely sure that it would be correct 100% of the time. In the case at hand real world reflections are the same 100% of the time.