This Cokin P121 G2 Hard-Edge Graduated Neutral Density 0.9 Filter is designed for use with a Cokin P Series Filter Holder. It 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 hard-edged line of transition between the dense and clear areas. A neutral density filter with a hard-edged line of transition is useful for images which include defined horizon lines. Neutral density filters do not affect the colouration of the image and this filter provides up to a 3-stop reduction in light from entering a lens.