Polarizers provide color and contrast enhancement. Reflected light often shows up as whitish glare that washes out color in an image. A Polarizer corrects this problem producing deep, dramatically blue skies. It also removes glare from non-metallic surfaces, such as windows and water. Color saturation in general, especially outdoors, can be improved significantly.
A Circular Polarizer has the same effect as a Polarizer and is used on cameras with beam splitting metering systems commonly found on auto focus SLR's (for most 35mm auto-focus cameras see your camera manual).
Area of sky most effectively polarized with a Circular Polarizer: Point your index finger at the sun. With your thumb extended at a right angle (90 degrees), rotate it around the axis of the index finger. It will point out the band of deepest blue from horizon to horizon.
For Circular Polarizer, see model CPF-34.