B+W offers screw on graduated ND filters designated (701M) and (702M) in a rotating mount, similar to that of a polarizer. These filters darken the respective portion of the subject by one or two f-stops without altering its colors. For example, when the sky is too bright in relation to the landscape, these filters are ideal for good detail rendition in the clouds and for preventing
the sky from being "washed out" by over-exposure. Because of the increased difference in brightness, it is important for the horizon line not to be positioned too far from the center of the image. These filters are made of Optical Glass with Multi-Resistant Coating (MRC).