Polarizing Filter, part 5

In my last post about the circular polarizer, I showed how the polarizer cut into the corner of the frame at 18mm. I should have qualified that observation with the fact that the polarizer was placed in front of a Neutral Density filter. At 18mm, not much can be added in front of the lens. A wall of maybe half a centimetre is about the maximum. Below is an 18mm shot with just the polarizer on -- the ND filter and the petal are on the table. The darkened corners are gone.