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. Wide Multi-Coated Circular PL It reduces the glare and reflections from glass and water and other non-metallic surfaces. It deepens blue skies, and saturates the colors. The Sigma circular PL filter is designed to give best performance with AF Cameras. The Sigma wide multi coated circular polarizing filter is very thin, so it does not cause vignetting with wide-angle lenses. You can monitor the changes at different angles through the viewfinder as you rotate this filter.