The NiSi 100 x 150mm Nano Medium-Edge Graduated IRND 0.9 Filter is a rectangular filter that helps to darken specific areas of an image such as bright skies, while allowing for a normal, unaffected exposure in the other regions of the image. The filter is densest at the edge and tapers to clear by the middle, with a medium-edged line of transition between the dense and clear areas. A neutral density filter with a medium-edged line of transition can filter the sky while minimizing its effect on the land. It is particularly useful for images that include elements like rooftops and mountains that protrude into the sky. Neutral density filters do not affect the coloration of the image and this filter provides up to a 3-stop reduction in light from entering the lens.