The Heliopan 49mm Variable Gray Neutral Density Filter is a solid variable neutral density filter providing a reduction of about 1 to 6 stops. The 0.3 to 1.8 density creates a darkening of the entire image, allowing you to photograph with a wider aperture or slower shutter speed than normally required. The degree of density is easily controlled by rotating the front filter ring, allowing you to previsualize the additional exposure length required. By slowing your exposure time or increasing your aperture, you are able to control depth of field and convey movement more easily. Neutral density filters do not affect the coloration of the image. Depending on the focal length of the lens this filter is not recommended for use with very wide angle lenses. Best results are achieved with manual setting.