The Hoya 67mm Pro ND 4 Filter absorbs the light entering the lens evenly
across the visible spectrum and reduces the light entering the lens by
up to 2 f/stops without affecting the colour balance. Reducing the
amount of light allows the use of wider apertures and slower shutter
speeds for creative and dramatic effects. ND filters are widely used by
landscape photographers who want to capture smooth, flowing waterfalls
or seascapes but still retain the correct exposure throughout the whole
photograph. Alternatively, ND filters can be used to reduce the depth of
field and enable the use of wider apertures to ensure your subject is
crisp while the background becomes a soft blur – great for portraiture.
ND filters also allow cine and video cameras (which have fixed shutter
speeds) to film subjects such as snow, sand or other bright scenes which
would normally cause over-exposure.