The 85mm Neutral Density 2.1 Filter for Cokin P from Hitech has several uses and offers the possibility to achieve otherwise unachievable results. It enables the shooter to adjust exposure without affecting color balance. A ND filter appears gray and reduces the amount of light reaching either the sensor of a digital camera or the film plane of a traditional film camera. A Neutral Density filter is also used to create some unusual special effects such as capturing the "blur" of the rippling water of a waterfall or the swirling effect of city traffic.
Since it allows the use of slower shutter speeds in bright light, it becomes possible to create these special effects that would normally not be possible to capture without the filter. And, since it can also help to control your depth of field, it permits you to shoot at wider apertures. Ultimately, its value is in helping to prevent bright, overly washed out images shot in bright light.