The Laowa Ultra Slim ND1000 37mm Filter is a Neutral Density filter with a 1000x filter factor that provides a 10-stop exposure reduction. This ND filter reduces the intensity of light wavelengths that move through the lens to give you a more balanced image. When you slow your exposure time or increase your aperture, you have better control of the depth of field and can portray movement far easier thanks to the Laowa ND1000 37mm filter. Superior Design The Laowa ND1000 Filter was designed to fit perfectly with 37mm filter threads. With an ultra-slim design, the filter will not take up much space so you can keep your lens lightweight. The ND1000 filter provides 10 stop exposure reduction for more balanced light intake.