The Tiffen 77mm Water White Glass NATural IRND 2.1 Filter is a neutral density filter with a 128x filter factor that provides a 7-stop exposure reduction. Its 2.1 density creates a darkening of the entire image, allowing you to photograph with a wider aperture or slower shutter speed than normally required. By increasing your aperture or slowing your exposure time, you are able to control depth of field and convey movement more easily. Neutral density filters are intended to not affect the coloration of the image and are ideal for pairing with other filters.