The Tiffen 4 x 4" 1 Red Soft-Edge Graduated Filter helps to specifically add a warm, bright red 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 soft-edged transition between the density and clear areas. The 1 color density provides less red coloration than the 2 density filter.