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.
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