The ProMaster Variable Neutral Density filter allows total lighting control in virtually any environment. Completely variable from a factor of ND3 to ND400. This filter is available in sizes from 37mm - 82mm 

Neutral density filters are designed to reduce the amount of light entering your camera lens and should not have any other effect on the image. Reducing the amount of light allows for the use of wider apertures or slower shutter speeds for creative and dramatic effect in bright lighting conditions.