Neutral density filter with a soft graduated transition between dark and clear areas, used for natural sky exposure control.
Technical Details
Standard sizes range from 77mm screw-in filters to 6x6 inch drop-in filters for matte box systems. Filter density is indicated in f-stops: 0.3 ND corresponds to 1 stop, 0.6 ND to 2 stops, 0.9 ND to 3 stops, and 1.2 ND to 4 stops of light reduction. The transition area typically extends over 15-25% of the filter height. High-quality versions use Schott B270 optical glass or resin material with multi-coating to minimize reflections and color casts. The filter thickness is usually 2mm for glass filters or 1.5mm for resin variants.
History & Development
Graduated ND filters originated in the 1960s from landscape photography, when photographers like Ansel Adams needed to solve exposure problems between the sky and the foreground. Cokin introduced the first modular drop-in filter system in 1978, which also included soft graduated filters. Tiffen established professional 4x4 inch filters for film productions in 1985. Lee Filters revolutionized the market in 1992 with resin filters, which were lighter and more affordable than glass equivalents. Since 2010, manufacturers like NiSi have offered magnetic systems for faster filter changes.
Practical Use in Film
Roger Deakins used soft 0.6 ND graduated filters in "Skyfall" (2012) for the Scottish Highlands sequences to preserve sky details without creating harsh transitions. In exterior shots, the filter is positioned so that the dark area covers the sky, while the transparent part leaves the foreground unchanged. The soft transition is particularly suitable for irregular horizon lines with mountains, trees, or buildings. In post-production, soft graduated filters are harder to emulate than hard ones, as the natural transition is mathematically more complex.
Comparison & Alternatives
Hard graduated ND filters have an abrupt transition over 2-5mm and are suitable for straight horizons like seascapes. Reverse ND filters have the highest density at the horizon and become darker towards the top, ideal for sunrises and sunsets. Digital alternatives include HDR shooting or exposure blending, but require longer post-production time. Variable ND filters offer stepless adjustment, but can produce color casts and X-pattern artifacts at strong polarization, making graduated filters indispensable for uneven lighting.