helpful when your test print is far from being correct.
When using a ring around, you should match the test
print as closely as possible to one of the prints. The
amount and color of filtration you should add or subtract
from the filter pack are the same as indicated on the ring
When the test print is reasonably close to being
correct, you can predict the final exposure conditions
accurately. Once again, remember how exposure affects
the three dye layers of the paper. That will simplify the
choice of selecting the correct filtration.
Color Printing Viewing Filters
When a test print is reasonably close to the desired
color balance, viewing it through color printing viewing
filters helps to determine what color change is needed.
Color printing viewing filters come in six filter colors:
red, green, blue, cyan, magenta, and yellow. Each color
is represented in 10, 20, and 40 density values.
To use a filter, hold it several feet away from the
print and light source. Quickly flick the filter in and out
of your line of vision to see the color correction the filter
makes. Since these filters tend to overcorrect the
highlights and undercorrect the shadows, you should
view the lighter middle tones through the filters to
determine the desired color balance. Try several filters
of different values and colors when evaluating a test
print; for example, when the print looks "cold" to you,
evaluate it through a series of red, magenta, and yellow
filters to determine whether the color in excess is cyan,
green, or blue. Similarly, viewing a "warm" print
through cyan, green, and blue filters will determine
whether the color in excess is red, magenta, or yellow.
Since the contrast of print materials is fairly high, a
filter used in exposing a print tends to produce a greater
change in color balance than the visual effect of viewing
a print through a filter. In general, the filtration change
to the filter pack should be one half of the viewing filter
that makes the lighter middle tones of the test print
appear correct; for example, you have determined that
when viewing a test print through a 20CC green filter,
the color balance looks correct; therefore, you would
make a 10CC change to your filter pack
Suppose, again, that the test print is too blue; that is,
not enough yellow dye was produced. The print will
look best through a 10CC yellow filter. Since blue light
creates yellow dyes, we must increase the amount of
blue light reaching the paper by 05CC. You should do
this by subtracting 05CC of yellow filtration (for
subtractive printing) or subtracting 05CC of blue
filtration (for additive printing). When a 20M filter is
best for viewing, subtract 10CC G (additive printer) or
10M (subtractive printer) from the pack to produce the
desired correction.
Remember, you must produce a test print with
proper density before you change the filtration on your
enlarger or printer. Before modifying the filter pack in
the enlarger or printer, you must keep in mind what type
of printer you are using. Modifying the filter pack for a
subtractive type printer is completely opposite from the
filter pack adjustment necessary on an additive printer.
Subtractive Printers or Enlargers
When you have determined what color dominates
the test print, that filter or its complement must be added
or subtracted from the filter pack Whenever possible,
you should subtract filtration.
adjustment should be made.
The following rough guide may also be helpful:
When a slight shift in color balance is needed, use an 05
or 10 filter change; when a moderate shift is needed, use
a 15 or 20 filter change; and when the shift required is
too large to estimate, try a 30 filter change.
The filter pack should not contain more than two
colors of the subtractive filters (yellow, magenta, or
cyan). When all three colors are in the filter pack neutral
density results. Neutral density only increases the
exposure time required. Neutral density is eliminated by
removing the filter color of least density completely and
then removing the same amount of density from each of
the other two colors. Thus, if you calculated the filter
pack to be 30M + 20Y + 10C, you should remove 10
CCs of each color (10C + 10M + 10Y) completely for a
filter pack of 20M + 10Y + OC.
When you either add or subtract filtration from the
filter pack, the intensity of the light also changes. When
filtration is added to the filter pack, the intensity of the
light reaching the paper is less. When filtration is
subtracted from the filter pack, more illumination
reaches the paper. Thus you must adjust the exposure
time when the filter pack is changed.
Fortunately, when dichroic filters are used, little
exposure compensation is needed. When these filters are
used, no correction is required when the yellow filtration
is changed. Only a l-percent change to the exposure
time is required for each 01 unit of magenta or cyan

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