Polarizer filter question

Can someone please tell me what the adjustable ring on my polarizer filter is for? It seems to just turn freely and I am not at all sure what the purpose of this is.

Thanks

Think of a polarizer as a device with a lot of 'optical slits' all parallel. When omnidirectional light passes thru, the rays which run parallel to the slits go thru, the rays which run perpendicular to the slits get blocked. The result is that reflections (polarized light) get blocked if oriented perpendicular to the slits in the filter. The ring allows you to orient the slits in the filter.

Thanks, that makes sense...but how do you tell which was they are oriented? It looks all the same to me.

You'll be able to see the effect through the viewfinder. Just point the lens at a window with reflections and twist the filter while looking through the viewfinder and you'll see the effect come and go. Depending on your angle to the sun, you'll also be able to see the effect on the blueness of the sky.

There is no real setting on a polarizer, no right or wrong, "this way up", or anything like that. As was mentioned, you decide if you need it or not, install it if you do, then just turn it and look through the viewfinder to get the effect you want.

Thanks all...makes sense now