The NiSi 4 x 5.65" Nano IRND 1.2 Filter is an ND filter with a 16x filter factor that provides a 4-stop exposure reduction. Its 1.2 density creates a darkening of the entire image, allowing you to photograph with a wider aperture or slower shutter speed than normally required. By slowing your exposure time or increasing your aperture, you are able to control depth