Graduated Neutral Density Filter

Fog, Sunrise Babler State Park, Missouri 1/22/2018

Fog, Sunrise Babler State Park, Missouri 1/22/2018

A graduated neutral-density filter, also known as a graduated ND filter, split neutral-density filter, or just a graduated filter, is an optical filter that has a variable light transmission. Typically half of the filter is of neutral density which transitions, either abruptly or gradually, into the other half which is clear. It is used to bring an overly-bright part of a scene into the dynamic range of film or sensor. For example, it can be used to darken a bright sky so that both the sky and subject can be properly exposed. ND filters can come in a variety of shapes and sizes and densities and can be used in all types of photographic applications from still photography, motion photography and scientific applications.

Although the importance of graduated ND filters may have lessened with the advent of the modern digital darkroom, graduated ND filters are still an important tool for professionals because a digital sensor that is clipping (“blown out” or “washed out”) captures no usable data in the clipped area, an effect which cannot be corrected with later processing because data has been lost.