A circular polarizer is a type of filter used in photography and videography to reduce glare and reflections from surfaces like water and glass. It works by allowing only light waves that are oriented in a specific direction to pass through, enhancing color saturation and contrast in images. This filter is particularly useful for capturing landscapes, as it can make the sky appear bluer and clouds more defined. Circular polarizers are often preferred over linear polarizers because they are compatible with modern camera autofocus systems and light metering technologies, ensuring accurate exposure and focus.