The Alan-Gordon Enterprises Blue Gaffer's Glass is designed to assist professional lighting designers during setup. The pocket-sized lens has a neutral density rating of 3.8 and is held up to one's eye giving users a clearer picture as to how the shot is lit. The glass can also reveal the location of the sun behind clouds. Additionally, the Gaffer's Glass is ideal for revealing the condition of tungsten light filaments. The glass can be useful in finding the center of your light output Useful for finding position of the sun when it is behind clouds