Tiffen’s 4 × 5.6 Ultra CP White Water Glass Filter is a specialty filter that polarizes light a little more than the usual polarizing filter. It removes unwanted reflections from non-metallic surfaces like glass or water, saturates colors for higher contrast, and makes deep blue skies appear even bluer. You can rotate this filter to adjust its effect, as its filter factor varies depending on how it’s rotated and its orientation to the sun.