105mm Screw Rotating Polariser Glass.
This polariser is attached to the filter system by an Accessory Ring (SOLD SEPARATELY), which fits to the front of the filter holder. This allows the polariser to be rotated independently of any other filters in the holder. It is the ideal solution for landscape photography, where a combination of graduated filters and polariser may be required.
The polarising filter is an invaluable tool in the photographer's armoury. Not only does it remove potentially distracting reflections from non-metallic surfaces such as glass and water but it also increases colour saturation and deepens blue skies, making white clouds stand out in sharp relief.
A polarising filter will increase your exposure by 1Ã¢â€¦â€ stops.
Linear or Circular? (...and we're not talking about the shape)
There are two types of polarising filter: linear and circular.
These terms do not refer to the shape of the filter, but rather the way in which the filter modifies the light waves that pass through it.
The type of filter required depends on the camera. If you use an autofocus SLR (digital or 35mm) in, for example, spot metering mode, you will need a circular polariser. This is because a linear polariser will interfere with the complex metering and AF systems of modern cameras.
If you use a manual focus camera, whether 35mm or medium format, you can use either a circular or a linear polariser. If you are still unsure of the type of polariser you require, check your camera's instruction manual.