A circular polarizer/linear (CPL) filter is a landscape photographer’s best friend.
The circular polarizing filter imparts a cyclic variation of the orientation of the electric and magnetic forces to the non-polarized light, selecting the appropriate component. It appears dark and absorbs light in front of the camera lens.
The CPL filter first polarizes the light by selecting a polarization plane. Then it depolarizes it again.
As a first and most important effect, the polarizer helps you remove reflections.
A CPL filter will return transparency to a body of water. This removes reflections and gives you a higher-quality image. You’ll be able to see the bottom of a sea or lake.
A CPL filter is also great on any type of glass. It will get rid of the reflection, making the objects behind the glass visible. Think of paintings or exhibits, for example.