All over ND standards are another filter that can be classed as essential in modern photography. These filters absorb light evenly across the visible spectrum, therefore reducing the light entering the lens without affecting the image color. Traditionally used on film for extending shutter speeds in bright conditions, they are now becoming essential to digital photographers for reducing the sensitivity of sensor chips on cameras which have relatively high minimum ISO settings.
Extending exposure times allows for movement in an image, be it people, water, foliage or clouds. The effects, if used with care can be impressive.