B+W Kaesemann Circular Polarizer

B+W Kaesemann Circular Polarizer

  • $149.95
  • Save $146


Size:72 mm

Product Description

Circular polarizing filters are made 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. The "high-end" polarizing foils of the Käsemann-type filters are neutral in color, they have a higher efficiency than conventional polarizing foils and they are cemented between high-grade plane-parallel optical glass. The resulting sandwich is then precision-polished again to achieve highly accurate plane-parallel surfaces. Subsequently they are edge-sealed to protect the foil against humidity. Discriminating photographers regard the B+W Käsemann-Type Polarizing Filter to be the very best of all polarizing filters. They are well suited for applications that require the highest possible imaging quality, especially with high-speed telephoto lenses and apochromatic lenses.

From the Manufacturer

Käsemann Circular Polarizers - The Highest Quality Polarizer Available

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.

Circular polarizing filters are made 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.

Käsemann polarizing foils are neutral in color, have a higher efficiency than conventional polarizing foils, and are cemented between high-grade plano-parallel optical glass, using a special cementing technique that resists delamination in humid climates. The resulting sandwich is then precision-polished again to achieve highly accurate plano-parallel surfaces. Discriminating photographers regard the B+W Käsemann Polarizer as the very best polarizer on the market. They are well suited for applications that require the highest possible imaging quality, especially with high-speed telephoto lenses and apochromatic lenses.

B+W Polarizers increase color saturation and reduce reflections. The filter factor varies according to how the filter is positioned in relation to the sun. Exposure compensation is about two f-stops.

Why Use a Circular Polarizer?

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. That's why you need a circular polarizer with such cameras. The circular polarizer circumvents this problem by adding 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.

MRC - A Special Scratch-Resistant, Water and Dirt Repelling Coating

The left half of this filter has a
traditional coating. The right half
has MRC coating.

The lens elements of high-quality lenses and the plano surfaces of filters require a perfect shape and smoothness to achieve the best optical quality. Dirt, greasy fingerprints, water marks and scratches reduce the image contrast and the sharpness, which can result in blooming at light sources and have an effect similar to a soft-focus lens. A clean front lens element and clean filter surfaces are therefore an absolute pre-requisite for demanding photographers.

MRC coating causes water
to bead up and slide right off.

The MRC coating is first and foremost a broadband anti-reflection coating. This means that its reflection-reducing effect, which is thus also a transmission-increasing effect, i.e. one which suppresses scattered light and ghost images and transmits more light, has a broadband action over the full spectrum. In contrast, the (almost always blue) single-layer coating only has a high effect in the medium wavelength range around yellow and yellow-green where the eye is most sensitive to light, while its effect is greatly reduced toward the blue-violet and purple-red end regions of the visible spectrum. With the MRC coating, this blue, violet and red to deep-red light cannot produce any contrast reducing scattered light, spotty reflections or ghost images. A broadband effect can only be achieved with a multilayer coating which requires a much higher effort and precision because unevenness and irregularities of the individual layers build up on one another and amplify one another. Schneider therefore uses a plasma-assisted evaporation coating process in which inert gas ions accelerated in an electrical field compact the material deposited on the lens surface in the vacuum chamber.

For photographers, the main advantage of MRC coating, is it's ability to combat flare and ghosting. An added benefit is that their filters remain free of dirt longer, so that they do not have to be cleaned so often. When cleaning the filter does become necessary, it is a lot easier to wipe off the dirt with a blower brush, because of MRC's ability to repel dirt and moisture. This also reduces the risk of micro-scratches which can occur during cleaning.

Side view of F-Pro Rotating
Mount.Click for larger view.

F-Pro Brass Filter Mount

This filter uses a rotating B+W F-Pro filter mount for added creative options. The mount has a front accessory thread and is made of brass. Compared to the earlier standard mount, the F-Pro mount, introduced in 2001, has become thinner. Now it can be used with wide angle lenses, including most 24mm focal lengths on a full frame body, without vignetting. Another advantage of the F-Pro mount is its modified retaining ring, which is no longer threaded in from the front, but holds the filter glass in place from the back. When removing a filter or lens hood that has been screwed on too tight to the filter, the retaining ring is not at risk of loosening.

  • This filter uses our standard B+W F-Pro filter mount, which has a front accessory thread and is made of brass.
  • MRC by B+W is not only an extraordinarily effective multiple layer coating, it is also harder than glass, so that it protects filters from scratches, and it is also water and dirt repellent, thus facilitating filter maintenance.
  • Manufactured from Water-White Schott Glass