Tiffen Rotating Circular Polarizer Filter - 40.5mm

This Tiffen Rotating Polarizer Filter - 40.5mm produces the same effect as a polarizer. It can be used on cameras with beam splitting metering systems, such as those on autofocus SLRs (35mm). You can rotate this filter to produce the desired effect you require. 

Polarizers are ideal for color and contrast enhancements outdoors. A Polarizer filter will correct the issue of reflected light which forms whitish glare and can wash out your image. Polarizers can remove reflections from water and glass, plus add richer, natural color saturation to your captured footage. They also create darker skies.

Tiffen offered this handy tip, regarding locating the 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°). You are forming an "L" shape with your fingers. Following the axis of your index finger (keeping the sun at the center point), rotate your hand towards your thumb. It will point out the band of deepest blue from horizon to horizon.