The Tiffen 5x5" Ultra Circular Polarising Filter is a remarkable filter designed to bring much more "punch" to your images. If a traditional polariser doesn't give you enough "oomph", the "Ultra" polariser offers you a little more. It will accentuate your blue skies even more - making the difference between a good photo and an exceptional image. Reflected light rays become polarised. Polarising filters are used to select which light rays enter your camera lens. They can eliminate unwanted reflections from non-metallic surfaces such as water or glass and also saturate colours, providing better contrast. The effect can be seen through the viewfinder and modified by rotating the filter. The filter factor varies depending on the filter's rotation and its orientation to the sun. Note: Circular polarisers are specially designed for use with autofocus SLR cameras (They will also work without any problems on manual systems and video cameras). - Your deep blue sky will become even "bluer" - A highly effective design - Made from Water White glass Specifications