Cooling filter
From The Glossary of Digital Photography
A filter placed on a camera or applied in software after photographing, to make the resulting image cooler, or bluer. The filter is blue and it lowers the cooler temperature of the scene as photographed. Filters of Wratten number 82, such as 82A, 82B, and 82C, are examples of cooling filters. These filters are usually used to correct the color of a scene to balance with the type of film used in analog photography; they are often used for creative effect in digital photography. A cooling filter is the opposite of a warming filter. See also warming filter
