Rotating front of circular polarising filters

No doubt a silly question - but gotta ask!

I was experimenting with my polarising filter on the weekend, and noticed that there can be a dramatic difference when the front is rotated. I can understand this effect with a linear filter, but if it's circular, why does this affect it?

Cheers!

I'm not sure I understand your question. You mean if you don't screw it on all the way it effects the picture? I just got my two filters today so I haven't tried the yet. Tomorrow! I got the Hoya HMC polarizing Pro1 and Hoya ND-8.

No, you will notice that when it is screwed all the way in the front can be rotated. This can be adjusted to give the required amount of polarisation, I believe. I'm just not sure why!

http://en.wikipedia.or​g/wiki/Polarizer

ALL polarizing filters need to be rotated to set the amount of the effect, regardless if they are "linear" or "circular". A circular polarizer is just a linear polarizer with a "quarter-wave plate" added to it. Check out the Index of Questions in this link for more information: Polarizing Filters