The Cokin Filter P164 Circular Polarization filter has special properties that are often used for special situations. Because the CP-filter is a bit bluer compared to a UV-filter, light loss occurs. It is therefore recommended not to use this filter indoors or in dark situations. The CP-filter can be used for taking landscape photos. By turning the filter you can influence the colour of the sky. You can decide how blue you want your sky to be. You can also influence the reflection of the water surface so that you can photograph "in depth". Another possibility is to remove reflection in windows.