which is sensitive to blue light, the silver halides in the emulsion of
polycontrast paper are "treated" so that some are sensitive to blue light
and others are sensitive to green. The green-sensitive halides affect the
low contrast portions of the print and the blue-sensitive halides affect the
high contrast regions.
This allows the paper to produce varying contrast
responses upon exposure to different colored lights.
instead of using different grades of paper, places one of a series of
colored filters under the projection printer lens to achieve a specific
(a) Up to ten filters may be available to permit the widest
possible contrast range.
The filters are numbered and, in the case of
Kodak's filter kits, range from 1 for very low contrast to 4 for very high
They range in color from yellow, for low-contrast, to deep
magenta, for high contrast. When a yellow filter (which absorbs some of the
blue light) is in place, a higher ratio of green to blue halides are exposed
thereby yielding overall lower print contrast.
The deeper the shade of
yellow the more the blue light is absorbed, causing lower contrast.
(b) On the other hand, when a magenta filter is used a portion of
the green light is absorbed and we get higher print contrast.
(c) With Kodak filters an average or normal contrast negative is
printed using a No. 2 filter. For a higher contrast negative use No. 1 or
perhaps a No. 0 filter.
For negatives which are slightly low in contrast
you might use a No. 2 1/2 or a No. 3 filter.
Paper - base, surface texture, weight, and size.
a. The base can be one of two types, fiber-based or resin-coated (RC).
There are advantages and disadvantages to both types.
(1) Fiber-based paper produces deeper black tones and more brilliant
whites than RC paper does. In addition, the image produced by fiber papers
will last longer than those of RC paper. However, fiber papers do require
the paper base, a greatly extended wash time is required to ensure archival
only four minutes for the wash. These papers are ideal for mass production
or when printing a rush work order.
RC papers are well suited for areas
experiencing water shortages or operations conducted in the field where
adequate amounts of water may not be available. Due to the lack of