This is a set of three graduated filters - Cyan, Yellow and Magenta - used to create special effects and to colour a chosen section of the image being photographed. By using these filters in varying combinations, red, blue and green effects can also be created. Additionally, effects can be achieved by using the filters in opposition to each other. The cyan, for example, could be on the top of the frame, enhancing the sky, whilst the yellow could be adding colour to the faded grass.