The B+W 40.5mm XS-Pro Digital ND Vario MRC-Nano Filter is a variable density filter that provides an exposure reduction of 1 to 5 stops. With a variable density of 0.3 to 1.5, the filter helps to darken the entire image and enables photographers to shoot with a wider aperture or slower shutter speed. The density of the filter can be adjusted by rotating the front filter ring, which helps photographers determine the additional exposure length required. It also features an MRC-Nano coating that acts as an anti-reflection coating and protective surface. The filter is constructed from Schott glass that ensures better optical clarity and color fidelity.