PolarPro ND256 | 4x565 Filter

Neutral density filter, takes light away so you can lengthen the exposure or open the aperture.

A neutral density filter takes light away without touching the colours. In daylight it lets you shoot wide open with a blurred background, film at 1/50 s by the cine rule, or lengthen the exposure until water melts into mist and people vanish from the frame.