The 77mm Tiffen SR Linear Polarizer is the most popular special effect filter available. Polarizers can create deep blue skies, provide a general saturation to all colors, reduce glare, and minimize reflections. Screw-in Polarizers are featured with rotating mounts for precise control of polarization. It can also be used as an adjustable Neutral density filter, with up to two stops loss with full polarization.
Tiffen Tip: Polarizing filters achieve different effects depending on the photographer's position to the sun. To get maximum darkening of the sky, the photographer stands sideways to the sun (shoulders point to it) with the sun fairly close to the horizon. As he or she turns toward or away from the sun, the darkening is lessened. When the sun is directly overhead, only a small part of the sky near the horizon can be darkened.
The Polarizer also removes unwanted reflections in highly reflective surfaces such as on cars or windows.