Product description Digitally Optimised (DG) Filters EX DG filters benefit from Sigma's multi-layer lens coating, developed to counteract the highly reflective characteristic of image sensors. With older style filters, light would reflect off the image sensor, bounce off the lens and filter elements and re-enter the image sensor, creating a ghost image. The multi-layer coating dramatically reduces this effect. In addition to this, an optimum, neutral colour balance is ensured, increasing the white balance accuracy of the digital camera. Circular Polarizing Filter This type of Polarizing filter has a large diameter and it also deepens the intensity of blue skies, eliminates glare. It not only reduces the reflection from non-metallic surfaces, but also increases colour saturation perfectly Amazon.com The Sigma AFI960 EX DG 86mm Single-Coated Circular Polarizer Filter is used to select which light rays enter your camera lens, and which light rays are reflected. This lens can remove unwanted reflections from non-metallic surfaces such as water or glass and also saturate colors providing better contrast. This effect can be seen through the viewfinder, and changed by rotating the filter, while the factor varies according to how the filter is rotated and its orientation to the sun. The Sigma AFI960 filter eliminates ultraviolet rays to remove haze from outdoor shots, as well as polarizing the light to remove reflections and increase color saturation, without affecting the overall color balance. This single-coated circular polarizer has an 86-millimeter thread size, and a filter factor between 2.3 and 2.8, which is approximately 1.3 f/stops. The AFI960 is constructed of high-quality optical glass, and is backed by a manufacturer's 1-year warranty.