Polarisers provide colour and contrast enhancement. Reflected light often shows up as whitish glare that washes out colour in an image. A Polariser corrects this problem producing deep, dramatically blue skies. It also removes glare from non-metallic surfaces, such as windows and water. Colour saturation in general, especially outdoors, can be improved significantly.
Essential general-use outdoor colour filter
Produces deeper skies and minimizes reflections in black and white and colour photography
Can be rotated to achieve desired effect
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).