The 4 x 5.65" ALPHA-I Solid Neutral Density 2.1 Filter from IDX System Technology is an ND 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 slowing your exposure time or increasing your aperture, 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.
To prevent internal ghosting and reflections, each glass surface includes multiple layers of anti-reflection coating. These coatings also offer greater protection to the filter substrate and help it to stay clean for longer than with uncoated filters. This filter is constructed from optical glass for clarity as well as color fidelity, and measures 4mm thick.