The NDx400 has a 9-stop light reduction equal to a ND optical density of approx. 2.7.
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.
* This filter is NOT suitable for solar photography. DO NOT look at the sun through this filter, eye damage will occur.