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Darkroom Filters
Dichroic  Filters

Photography (Basic) - Introduction to photography and other graphic techniques
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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







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