CPC 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.
Eliminates excess blue in sky, sea, high altitude and flash photography. Absorbes only 1/10th of an f-stop of light; Doubles as a UV filter and can be left on for lens protection.