CPL Filter Installation Question

[hnb48]

I purchased a CPL filter for my M6 Plus. It did not come with an arrow indicating installation direction as noted in other posts on the filter. My question is, does it matter which direction the filter is installed? I've looked through the filter from the back at a couple of different bright objects, digital picture frame and iPhone, and then rotate it 90-degrees. The view does go to full dark when I rotate it 90-degrees like a polarizer should react but when I rotate it back to normal camera position, up or down either direction, I really can't tell if it is actually reducing any reflections. Presently, I'm away from my car so I can't fit it temporally to see if it matters. I was just hoping to get some feedback before I get home and attach it permanently. For info, my camera is mounted on the dash rather than up high on the windshield .

 

[DT MI]

https://dashcamtalk.com/forum/threa...nt-how-to-adjust-diy.15022/page-2#post-197505

 

[hnb48]

Thanks for the link. Unlike other cpl filters, the M6 Plus filter already comes vertically aligned due to the way it mounts on the front of the dash cam (meaning turning it 90-degrees the view turns dark). So to me it now appears that top or bottom doesn't matter.

 

[DT MI]

...So to me it now appears that top or bottom doesn't matter.

That would be he case - maximum polarization occurs at 90 degrees so 180 or 0 degrees would have the same effect.

 

[hnb48]

Yep. Totally agree. Now it makes me wonder why so many of the cpl filters on the market have an arrow on them. It's impossible to put them on wrong.

Thanks again for your responses.