Filters for Color Printing

Table 3-7.–Safelight Filters Filter Designation Color OA Greenish Yellow Use With Black-and-white contact and duplicating materials and projection films OC No. 1 No. 1A No. 2 *No. 3 Light Amber Red Light Red Dark Red Dark Green Printing papers Blue sensitive films Orthochromatic copy films Orthochromatic films Panchromatic films NOTE *Use caution when processing panchromatic film under a No. 3 safelight. When a No. 3 safelight is used, the film should not be exposed to it until at least half of the developing time has passed. Then the film should be examined quickly at a distance of about 36 inches from the safelight. Much experience is needed to judge proper negative development by the process of inspection, and it is rarely performed. Yellow filters are used to print black-and-white negatives that are high in contrast. Variable contrast printing filters are discussed in chapter 10 of this TRAMAN. FILTERS FOR COLOR PRINTING Filters used to print color are as follows: color compensating (CC), color printing (CP), ultraviolet absorbing, and dichroic. Each one of these filters is discussed below. Color Compensating Filters The color compensating filters used for printing color materials are the same CC filters used with color film. These filters are used to modify the color quality of the exposing light needed to print the color negatives or transparencies. CC filters are used between the lens and the paper in the color printing process. These CC filters are referred to as a filter pack CC filters control the color of light that strikes the emulsion. They control the amount of light each emulsion layer receives during exposure. That results in the amount of color dyes formed in each emulsion layer. The overlapped colored dyes (cyan, magenta, and yellow in proper proportions) represent the colors of the original scene. Color Printing Filters Color printing (CP) filters are used in color printing, the same as CC filters with one exception. CP filters are placed in the enlarger between the light source and the negative or transparency being printed. That is done because CP filters are made of acetate and affect image definition. CP filters are available in red, cyan, magenta, and yellow with densities of 0.05, 0.10, 0.20, and 0.40. The color of a filter and its peak density are identified the same as CC filters. Ultraviolet Absorbing Filters Ultraviolet absorbing filters for color printing prevent the fogging of the color material by ultraviolet radiation emitted by the exposing light source. This filter is not considered part of a printing filter pack, but it is always present in color printing systems. An ultraviolet absorbing filter for color printing is identified as 2B. 3-11