A polarizing camera filter is a special attachment put on the end of the lens that affects the way light hits the camera sensor. A polarizing camera lens filter is made of two slices of glass, one that rotates and the other that doesn't. There are two types of polarizing filters: circular and linear. Linear polarizing lenses work best with manual focus cameras, while circular lenses are preferred for auto focus cameras. A polarizing camera lens filter has three main effects: to saturate colors, to reduce reflection, and to limit light.
Saturating colors
A polarizing lens filter saturates the colors in an image. Polarizing lens filters work best when they are pointed perpendicular to the sun's light. The amount of contrast can be increased or decreased by turning the filter up to 180 degrees. Any more than this simply repeats the already seen effects. This filter also leaves whites unchanged, which increases the contrast in the image. One of the most dramatic effects of using a polarizing lens filter is darkening blue skies while leaving the white clouds untouched.
Reducing reflection
Another powerful effect of a polarizing lens filter is its ability to reduce reflection in a photo. This effect is particularly useful when shooting through glass or into water. For example, using a polarizing lens filter allows you to take a picture of a fish in a tank that focused on the fish rather than your reflection. This effect is most effective when the camera is aimed perpendicular to the reflective surface. If you were to take a picture looking straight down at a river, for example, the water would be clear. The limitation of this filter is that it will not reduce glare from metallic surfaces.
Limiting light
The polarizing lens filter also limits the amount light that gets to the sensor by between a stop and a half to two stops. This can be beneficial because allowing in less light can decrease the shutter speed of the camera, which can be used for special effects photos, such as a photo of a rushing river. However, the camera cannot stop high-speed action, such as athletic events, as well as without the filter.
Drawbacks
The polarizing camera lens filter is not without its drawbacks. Because it is made of two pieces of glass, a polarizing camera lens filter is thicker than other lenses and can cause distortion on the edges of photos. Also, polarization can be uneven, so sometimes there will be great variation of the colors in the photo---in the colors of the sky, for instance.
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