Polarizers are used to reduce glare on reflective surfaces. They can be used to effectively enhance clouds against a blue sky or greens in grass or leaves.
approx. +1.3 stops
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. Circular polarizers are to be used with cameras that have a beam splitting metering system (most autofocus SLR'S)