Do circular polarizing filters come in various strenghts or ranges of change?  ARe all C-polarizing filters the same?  Yes, I know how to use them. I know the 90degree angle to the sun and all that ...I feel that I should be able to rotate the filter and see through the lens excactly what the change will be...frankly I find it very difficult to see the amount of change in the blue of the sky using the filter that I have....shouldn't you be able to rotate the filter and observe the change gradations?  Shouldn't they be obvious as in a ND filter?  Should I ask for a "stronger" polarizing filter?