Often, you want to balance light intensity between two areas within a scene. A color grad neutral density filter helps to eliminate this problem. The half gray, half clear design allows proper exposure of both foreground and sky. Tiffen filters are manufactured using ColorCore technology, a closely guarded proprietary process that entails permanently laminating the filter material in between two pieces of optical glass that are ground flat to tolerances of a ten-thousandth of an inch, then mounting them in precision metal rings. The ColorCore process allows us to control the color and density of Tiffen filters, and the characteristics of special effects filters with much greater accuracy than typical dyed-in-the-mass filters, which usually exhibit color and density.