The Tiffen 4 x 4" ND 0.4 filter is a solid neutral density filter offering a 1.3-stop exposure reduction. This 0.4 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 down your exposure time or increasing your aperture, you can more easily control depth of field and convey motion. Neutral density filters do not affect image colouration and are ideal for pairing with other filters. This filter is manufactured using ColorCore technology, a process that involves laminating the filter substrate between 2 pieces of optical glass and grinding it flat to a tolerance of 1/10,000th of an inch. This filter measures 4 x 4" / 101.6 x 101.6 mm. Features: - The 0.4 solid ND filter darkens the image, allowing you to photograph with a slower shutter speed or wider aperture than normally required. - Offering a 1.3-stop exposure reduction, this filter allows you to more easily control depth of field and convey motion. - The filter does not affect image colouration and is ideal for use with other filters. Specifications: - Type: Solid Neutral Density - Size: 4 x 4" / 101.6 x 101.6 mm - Density: 0.4 (1.3 stops) - Effect: Allows longer exposure