The 55mm Slim Pro II ND 0.9 Filter from Haida is a circular ND filter with an 8x filter factor that provides a 3-stop exposure reduction. Its 0.9 density creates a darkening of the entire image, allowing you to photograph with a wider aperture or slower shutter speed than normally required. By slowing your exposure time or increasing your aperture, you can control depth of field and convey movement more easily. Neutral density filters do not affect the coloration of the image and are ideal for pairing with other filters. This Slim Pro II ND filter is constructed from optical glass for clarity as well as color fidelity. To prevent internal ghosting and reflections, the glass features eight layers of multi-coating. These coatings also offer greater protection to a filter substrate and help it to stay clean for longer than with uncoated filters. A thin, aluminum-alloy filter ring minimizes the potential for vignetting, while remaining durable and lightweight.