Tuesday, April 15, 2008

Circular Polarizer:A photographer's friend

I use a polarizer(Hoya 55mm) on almost every shot with a blue sky. Without a polarizer, blue skies appear dull, light blue on film; with a polarizer filter, they come out in a rich, deep color. The filter works by cutting out reflected glare and it's also useful for water (lakes, ponds,rivers), window glass, and tree leaves. A polarizer is more expensive than most other filters but worth the investment.

Regardless of the type of shooting you do, a polarizer is the most useful and versatile filter you can own. It's a very visual filter with which to work: As you rotate it in its mount, the effects are immediately noticeable. A polarizing filter can deepen the color and contrast in a sky (the most intense effects are always 90° from the sun or light source), eliminate glare from wet or reflective surfaces and cut through atmospheric haze to increase clarity and contrast in a scene. Since the effect of a polarizer is most pronounced when it is used perpendicular to the light source (the sun usually), try this trick... Make an "L" with your thumb and forefinger. Point your forefinger at the sun and your thumb will point in the direction that the polarizer will have its greatest effect. You can rotate your thumb around the axis of your forefinger, pointing the lens in any of these directions will let you take full advantage of the polarizers capabilities. Polarizers have little or no effect when they are used in the same direction as the light source.

Polarizers come in two varieties: Linear and Circular. Each has the same effect visually; the difference is just in the way they polarize the light passing through. If you own an auto focus or auto-exposure camera (basically any modern camera), use a Circular polarizer, which won't interfere with its automatic functions. Digital cameras in general do not have reflection mirrors, and, as a result, can use both (linear or circular) polarizers.

LINEAR
Produces deeper colored blue skies, which at the same time creates a striking contrast with white clouds. Minimizes light reflections from glass and water Reduces glare from non-metallic surfaces. Provides a general color saturation to both cool and warm tones. Can be used in extremely bright light situations to reduce the amount of light entering the camera; this enables more selective depth of field control. Manufactured in self-rotating and drop-in formats. Note: using a Linear Polarizer on an auto focus camera with a beam-splitting meter will result in under-exposure of approximately 2-3 f:stops. Light is polarized by both the filter and the beam-splitting meter which results in double polarization. However, Linear Polarizers can be used with both non-auto focus and auto focus video cameras.

CIRCULAR POLARIZER
Provides the same filter effects as a Linear Polarizer, but is designed to work with auto focus cameras with beam splitting metering. The Circular Polarizer has linear polarizer construction plus a built-in "Wave Retardant" to ensure proper exposure. The linear element polarizes the light, and the wave retardant de-polarizes it, and then the beam-splitting meter polarizes the light again for proper exposure. The use of a Linear Polarizer with a beam-splitting meter will result in underexposure. Also used in video for video assist. (video tap).
Light Loss: 2 f:stops

Courtesy:geocities.com/cokinfiltersystem/polarizer.htm

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