B+W Filters 77mm Neutral Density Filter0.3
Neutral Density Filters are used to reduce the amount of light entering the lens. This technique is beneficial for achieving a number of creative freedoms. For example, if a slow shutter speed is required for a a desired blur effect, this adjustment could wash out the frame with too much light. With a neutral density filter, the problem is solved. These filters can aid in controlling the depth of field as well.
Neutral Density Filters are designated a number to represent their optical density (based on how much light is absorbed).
ND 0.3 reduces the light entering the lens by 1 stop.
ND 0.6 reduces the light entering the lens by 2 stops.
ND 0.9 reduces the light entering the lens by 3 stops.
Neutral Density Filters are often available in gradations. The filter's optical density begins as 0.3, 0.6 etc and gradually becomes 0, or transparent. This is useful for eliminating “blown out” issues. For example, a perfectly exposed landscape might be accompanied by a sky so bright that close to no detail is registered. The side of the filter which has the greater optical density can be used to reduce the brightness of the sky, potentially capturing beautiful details in the clouds while maintaining the same exposure on the land below.