The Cokin hard-edge graduated fluorescent pink 1 filter can be used to enhance dull, flat, or hazy skies. The filter is densest at the edge and graduates to clear at the middle, with a hard-edged line of transition. Hard-edge filters are great for images with a defined horizon line. The filter is Rectangle so you can selectively choose where the pink edge sits in the framing of the image. The fluorescent 1 is lighter (1-stop) and creates a more subtle effect than the fluorescent pink 2 (2 2/3-stops).