Instruct: Classify Amazon reviews into positive or negative sentiment
Query: I can't tell if it works or not

A friend told me to get a circular polarizing filter for my canon lens so the sky here (which is always blue) would pop if there were any clouds. I needed a protective filter anyway so thought I'd try it. I really cannot tell the difference when I move the lens as to the difference in polarization. But, it is a protector for my nice canon lens, even though it is a bit too expensive than just a plain polarizer lens,for just that purpose.