Hoya Graduated 77mm Neutral Density Filter balances exposure between the lightest and darkest areas of a scene allowing better tone and detail to be recorded in these areas of the image. It is darker at the top giving that area a 3-stop light reduction and then fading evenly to a 1 stop light reduction at the bottom. This creates more balanced exposure between the lighter and darker areas of a scene, especially useful for photos that include the sky. The aluminum filter frame rotates so the darkest area can be positioned as needed.