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Circular Polarizers - Increase Color Saturation, Reduce Reflections

The images on the left was taken without any filter.
The image on the right was taken using a
B+W Circular Polarizer. Click for larger view.

The images on the left was taken without any filter.
The image on the right was taken using a
B+W Circular Polarizer. Click for larger view.

Highly efficient standard circular polarizing filter for all cameras with beam splitters in the light paths of their TTL exposure meter and with autofocus lenses. Circular polarization has the same pictorial effect as linear polarization, but allows for proper exposure metering and/or autofocus distance settings.

B+W Polarizers increase color saturation and reduce reflections. The neutral gray color and plane parallel polarizer material guarantee optimal image results. High-quality optical glass ensures excellent pictorial quality. The filter factor varies according to how the filter is positioned in relation to the sun. Exposure compensation is about two f-stops.

Linear and circular polarizers both consist of a linear polarizer foil but differ in their construction in the following way. Modern DSLR cameras have a beam-splitting prism that sends part of the incoming light to the meter and part to the viewfinder. The effect is that the light entering the meter is partially polarized by the beam-splitter. A linear polarizer placed on the lens of such a system will act as a second polarizer and block light to the meter by a degree dependent on the angle between the prism and the polarizer on the lens. The result is incorrect exposure/aperture values from the meter. The circular polarizer circumvents this problem through the addition of a 1/4-wave retarder, or delay foil. This ensures that the linearly polarized light is changed into a rotation that appears unpolarized to the meter, resulting in proper exposure/aperture readings.

Uncoated for Greater Effect

The glass of this filter is uncoated. This is common with special effects filters, where coating is either an impossibility or would work against the effect the filter is trying to attain.

Side view of Slim Line Rotating
Mount. Click for larger view.

Slim Line Filter Mount

This filter uses a rotating Slim-Line mount made of aluminum for wide angle lenses. They do not have a front accessory thread to avoid vignetting with lenses as wide as 17mm in 35mm format. Some report success with lenses as wide as 16mm. A slip on cap is supplied.

Because this is a rotatable polarizing filter, it has a height of 5mm.