Brightness 133 FIGURE 6.6 Inverse square law (law of squares). If a square surface of 1 ft. Â 1 ft. is illuminated to 120 FC 10 ft. from the light source, at 20 ft. the same amount of light is now spread over a 4-ft. Â 4-ft. area. The amount of light is therefore a quarter of what it was at 10 ft. (120/4 ¼ 30 FC) Fingers are used to reduce the intensity of a sliver of the beam. Dots are used to reduce the intensity of a very small circular area and can be used to even out hot spots in the center of beam field. Both come as single nets, double nets, silks, and solids. Bobinette: Black net fabric that comes in bolts. It is handy, because it can be cut to any Fingers and dots: