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CPL Lens Adjustment

Can anyone tell me what the correct adjustment angle is for the CPL lens?

I rotated the lens in the frame as directed in a few YouTube videos I saw. I now have more glare than before I starting with. I have tried looking through the screen on my a119s while adjusting but it is too small to detect the glare with much accuracy.

Any help would be appreciated.



Find an LCD display such as smartphone, computer screen or TV that darkens the CPL at 90 degrees holding the plastic CPL frame with snap flaps pointing towards you. You'll have to slightly pop the lens from the wide slot so it will rotate easier. My video shows what a correctly aligned CPL should do when rotated.


Thank you for your reply, and your video is excellent.

I think I am all set with my CPL adjustment. 

The weird thing is that my lens darkens in different positions depending on what device I use to calibrate it.

For instance: on my computer monitor the lens darkens at 90% rotation, on my TV it blacks out at 45%, and it really doesn't darken nearly all the way on my on my ipod.

I'm not sure why or what the differences are between the devices.

Adjusting CPL filters usually isn't required but many are sold unaligned. A few years ago there were very few Dashcam Circular Polarizing Lens filters available, DIYers knew that old cheap flip phones included a thin Polarizing Lens Filter matrix layer under the glass screens, DIYers cut them to fit over their Dashcams, image quality suffered but dash reflections were eliminated. As you discovered when you attempt to adjust the CPL filter using any LCD display each devices screen produces a different CPL pattern when rotated. This is due to each device having its own Polarizing Matrix configured to either reduce glare from above or from sides, computer screens generally use 45 degree angle for Polarizing Lens Matrix to hinder side privacy viewing and glare. The LG smartphone used in video produces the full blackout effect for demonstrations, my Samsung phone doesn't darken at all instead turns slight green, my computers screens are all 45 degree which can be confusing but still works fine. Suggest you use the device that isn't 45degree. Pop out the CPL filter but do not flip it over, hold the CPL so the darkest view is produced looking through the lens, if its flipped its doesn't go dark as much as from other side. Once you determine the 90degree angle of darkest image rotate 90 degrees to brightest and mark top edge with marker. Insert back into plastic frame with marked edge showing at center of slot.
Now that I write this I should make another video detailing this procedure. You'll know the CPL isn't aligned because the vehicle dash reflection will appear in your video clips on left or right side.


Created this CPL Alignment video after noticing dash reflections reappearing in dashcam clips caused by the CPL shifting after one year of use. The Alignment method in this video uses the Dashcam's LCD screen for a quick and easy DIY adjustment.

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