I was having a talk to an optometrist the other day about polarising filters and we got into the topic of which direction the filter actually runs in the lens.

Now, correct me if I am wrong, but I was taught that even though the axial marks on the side of a polarising filter before you cut it run at 180 degrees, the filter itself runs at 90 degrees thereby cutting out the plane reflected light at 180 degrees (eg like in one of those "Nu-Polar" polarising kits that has the fluro tube sitting above a flat piece of glass, and by putting the filter infront of your eyes you take out the reflected light travelling in the 180).

The Optometrist seemed to think that for some reason, the filter was set at 45 degrees. The problem I see with this theory, is that you could very easily have one set at 45, and the other set at 135, while still cutting the lens with the axial marks at 180 degrees.

So after all that, if anyone can understand my ramblings, am I correct?