The 58mm ND Fader Filter from Genus is unique in the world of neutral density filters. Other companies make you buy individual ND filters to meet your needs (i.e. 1-stop, 2-stop, etc.). Genus provides one filter that generates 2-8 stops of neutral density depending on how it is rotated.
In addition, the filter is indexed so you know exactly how many stops of neutral density you are getting. It screws on like any other filter and with a mere twist of the convenient rotating handle on the filter ring, you dial in your filtration. No need to constantly change filters - as the light changes, just dial in another grade of filtration.
Neutral Density filters have several uses and offer the possibility to achieve otherwise unachievable results. They enable the shooter to adjust exposure without affecting color balance. ND filters appear gray and reduce the amount of light reaching the film.
Neutral Density Filters Have Four Main Uses
To enable slow shutter speeds to be used, especially with high speed ISOs, to record movement in subjects such as waterfalls, clouds, or cars
To decrease depth of field by allowing wider apertures to be used, which helps separate subjects from their background
To decrease the effective ISO of high speed film (above ISO 400) and allow it to be used outdoors in bright situation
To allow cine and video cameras (which have fixed shutter speeds) to film subjects such as snow, sand or other bright scenes which could cause overexposure