The Tiffen 4 x 5.65" 1 Cyan Hard-Edge Graduated Filter helps to specifically add a bright cyan coloration to skies and other bright areas of an image while allowing a portion of the image to remain neutrally colored. The filter's coloring is densest at the edge and tapers to clear by the middle, with a hard-edged transition between the density and clear areas. The 1 color density provides less cyan coloration than the 2 density filter.