The Genustech POLARIZER ND Variable Filter uses two independent rotating rings to control light and also achieve perfect Polarization. The first rotating ring is used to fine tune the light entering the lens. By slowing your exposure time or increasing your aperture you are able to control depth of field and convey movement more easily. The second rotating ring has the Polarizer element. By adjusting this ring you will filter out glare and reflections as well as achieving greater saturation of skies and foliage.