B+W 49mm #106 SC Neutral Density 1.8 6-Stop Filter
The B+W 49mm #106 SC Neutral Density 1.8 6-Stop Filter reduces light entering the camera by six f-stops. With this filter, and without changing the aperture (and DOF), an exposure time of 1/60 s becomes a full second. Running water is rendered hazy and soft. A tripod is necessary in any case.
*Please Note: ND filters must not be used for direct visual solar observation (risk of blinding). They let through UV- and IR-rays which harm the eyes. Special sun filters for direct observation of the sun are available from astronomy suppliers.