Split Filtration Exercise - Stephen Grote

Split Filtration
Split filtration is a feature of Variable Contrast (VC) enlarging papers and filters. It is the
ability to use different contrast grades on a single sheet of enlarging paper. Variable Contrast
papers have two blended emulsion layers, one for high contrast and one for low contrast. This
allows the printer to control both the highlight and shadow details on the same sheet of paper
which adds a subtle richness to the print.
Using split filtration is easy. Make zebra test strips the length of the print using the a high
contrast filter (#3 through #5 filters) in one second, two second, three second or five second
increments. Look carefully to see where the black goes extinct and fades into white. The time for
the high contrast filter is the time on the test strip before the black/gray fades to white.
Now make your normal print with a #0 through #2 filter, which ever contrast grade is more
appropriate for the image. Experimentation may be necessary to find the right contrast grade and
the appropriate time for the image.
You now have the two components needed to effectively use split filtration. Place the paper in
the easel and expose it with the high contrast filter at the proper time. Then, leaving the paper in
the easel switch filters back to the normal or low contrast grade filter (usually a #0, #1 or #2) and
make your exposure. Develop the print and compare it to the previous normal print. The blacks
should be darker creating an effective contrast boost in the scene. If the exposure turns out too
dark you will have to reduce the exposure on the normal or lower contrast filtration.
Using the split filtration method you can add more contrast simply adding more time to the
high contrast filter exposure and taking time away from the lower filter to get the appropriate
exposure. If you need to lower contrast then reduce the time on the high contrast filter while
adding time to your lower contrast filter exposure or switch to a lower number contrast filter.
Remember to keep good notes, especially on times and filtration as well as dodging and burning
information.
Why use the high contrast filter first? There have been many arguments over which filter to
use first. Both filters effectively flash the print or pre-expose the paper, but if the lower contrast
filter is used first the exposure threshold of the paper is generally broken on the lower contrast
end and may veil the contrast in the print by adding density to the highlights (whites). Using the
higher contrast filter first, especially in moderation, the exposure threshold of the paper is not
broken on the lower contrast end and both filters work together to raise the contrast in the
shadows areas (deepening the dark areas, yet retaining the detail) while maintaining lower
contrast in the highlights (retaining the detail in the whites).

There are several methods of utilizing split filtration. There is no one right way. I have seen
split filtration written about in several publications and each has it own twist to it. Some printers
find that using the low contrast filter first works better for them, others claim that using the
higher contrast filter first works better for them. Find the method that works best for you and
keep good notes. Remember that the low contrast filter is considered to be the highlight printer
(controls your highlights or whites) while the high contrast filter is considered to be the shadow
printer (controls your shadows or blacks). When looking at your test strips ask yourself the
questions: How low can I go with my contrast and not have my highlights look muddy? How
high can I go with my contrast and not have my shadows too dark?
Contrast filters block the light of its opposite color. The low contrast filter is yellow and
blocks blue light or high contrast light. The high contrast filter is magenta and blocks green or
low contrast light.
If you intend to demonstrate the split filtration technique make five prints. One zebra test strip
for the high contrast filter, one full print with the high contrast filter only, one zebra test strip for
the low contrast filter, one full print with the low contrast filter only and one complete print
utilizing both the low and high contrast filters. Dodge and burn (harmonize) the last print as
needed.
Split Development
Split Development works much the same way as split filtration. Split development is most often
used to lower the contrast of graded papers by using two developers - a low contrast developer
and a high contrast developer. Lowering the contrast of graded papers can be done by using the
low contrast developer first to keep the blacks from becoming too dark, then at the very end of
development (the last 15 to 20 seconds of a two minute development) gently move the print into
the high contrast developer to increase the density of the shadows.
In our case, the low contrast developer is generally referred to as a warm tone developer or a
developer with only Metol (Elon) or Phenidone as the developing agent. The high contrast or
normal contrast developer will include Hydroquinone, Chlorohydroqunione, Glycin, Amidol or
Pyrogallic Acid (commonly referred to as Pyro) in addition to the low contrast developing agent
Metol (Elon) or Phenidone.
Please note that there are high contrast or normal contrast warm tone developers. Do not be naive
and think that all warm tone developers are low contrast developers.
Make sure that you have the higher contrast developer in the second tray and do not leave the
print in the high contrast developer for any more than 20-30 seconds or you will increase your
contrast level too high to have noticed the difference.