The Tiffen 4 x 5.65" 4 Yellow Hard-Edge Graduated Filter helps to specifically add a warm, bright yellow 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 4 color density provides less yellow coloration than the 5 density, but more than the 3 density filter.