Polarizing filter

... and look for what? I know from my photography with circular polarizers that turning them will change the appearance of the sky, which has polarized light, but I never found it made a difference in anything else. The image I get from the Garmin filter in the "obvious" position seems to work fine.
 
CPL's are used on dashcams to reduce reflection from the dashboard area, not to make the sky look better
 
They reduce reflection and glare, and it typically doesn't matter how you align them for that. But it's worth experimenting if you're not happy with the default position. I found it pretty much eliminated dashboard reflections.
 
jonat said:
They reduce reflection and glare, and it typically doesn't matter how you align them for that. But it's worth experimenting if you're not happy with the default position. I found it pretty much eliminated dashboard reflections.
Click to expand...

if you have a filter that is preset to the correct orientation or marked so that it can be aligned to a predetermined orientation then no need to move it, they will only reduce reflection in one of either of two positions (180 degrees from each other), rotate them away from that and you'll get increased reflections, anyone that doubts this can spin the filter around and see for themselves what effect it has at various positions, @lacibaci mentioned previously using a sheet of white paper on the dash, this is a good way to note the difference
 
Oh, I see now. Use the paper to check for reflections. That wasn't clear to me. Ok.
 
jonat said:
They reduce reflection and glare, and it typically doesn't matter how you align them for that. But it's worth experimenting if you're not happy with the default position. I found it pretty much eliminated dashboard reflections.
Click to expand...

It does matter how you align them, because the reflections we're concerned with from the dashboard off the windshield are polarized light. If you align it wrong, you end up with virtually no blockage of the polarized light so it ends up appearing even brighter on your video
 
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