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CONTRAST CONTROL MASKS

Have you ever wondered why that print will not match the
transparency from which it was printed?
Although beautiful prints can be made from transparencies
directly or through an internegative, they will never be an exact
match. After hours and hours of printing and reprinting,
darkroom enthusiast give up and decide that they are not good
darkroom technicians. Life is easier and a lot more simple if a
person decides not to match the transparency exactly, but just to
make a good print.

The greatest problem is a law of physics. An image being
viewed with transmitted light can have a lot higher contrast
ratio without losing details in either the highlight or shadow
areas than an image being viewed with reflected light.
Whenever you go from one generation to another
(i.e., transparency to print, print to negative, transparency to
transparency, and yes, even negative to print), you run into two
large problems; an increase in contrast and colors overlapping or
contaminating each other.

In compressing the contrast range of a transparency with
very high contrast down to the contrast range of a reflected
light print, the details can be preserved by using a contrast
control mask. The mask is simply a low density black and white
negative that is sandwiched with the transparency for use
whenever the transparency is reproduced as a duplicate
transparency or print.

Making a contrast control mask can be simple, although there
are several ways of making a mask, we will discuss the easy way
that still does a very effective job.

Most people use Kodak Pan Masking film to make contrast
control masks, but other black and white films will work by
aiming at a low density, high contrast negative.
You do not want any details from the shadow areas of the
transparency to show on the black and white mask or, at the most
a very minimum. There should be density only in the highlight
areas (of the transparency).

In making the mask, it is best (and saves time) to use a pin
registration system. There are professional and more
sophisticated types available, but one can set up a system using
a hole punch from the office supply and plate maker's register
pins from the graphic arts supply.

First, punch holes with the punch in a thin piece of
cardboard. With the register pins in the holes of the cardboard,
tape the pins to a black surface (as non-reflective as possible).
Tape a piece of acetate to the edge of the transparency and punch
holes in the acetate. Punch holes in the black and white film
(naturally this has to be done in the dark). If film that is
smaller than 4"x5" is used, a piece of acetate with holes punched
in it can be taped to it.

Your set up for the exposure will look something like this:
Starting from the bottom;
1. A black non-reflective surface
2. The black and white film (emulsion up).
3. a 0.10 mm diffusion sheet (to facilitate registration)
4. The original transparency (or negative) on the
register pins (emulsion down).
5. A piece of CLEAN glass can be put on top to hold
everything flat.

The light source usually used is an enlarger. The correct
exposure must be determined by experimenting. The exposure will
be affected by the type of film used, the intensity of the light
source, the type of developer used, the time of development, etc.
The film that is used the most is Kodak Pan Masking film
developed in DK-50 developer. If these are used, you might start
your exposure (bracketing) at one second a F/16, F/11, and F/8.
The mask should look like a very thin black and white negative
with clear areas in the shadow areas.

After processing, the film is placed, with the transparency
on the register pins and taped together. They then can be
trimmed and put in a negative carrier to make a print or
Duplicate transparency, or mounted in a slide mount.
Even contrasty negatives can be helped with a mask. In
exposing the mask for the color negative, four CC50B filters
should be used between the light source and the negative. The
most drastic situation that I have ever dealt with was a shot of
an indoor swimming pool with a window for a wall.
The exposure difference between the outdoors and indoors far
surpassed the contrast range of the printing paper. The problem
can be solved two ways. (1)Make a line mask the size of the
print (which in this case was to be a 30"x40") or (2) make a
contrast decrease mask. By making the mask as described above
the print was made with all of the detail reproduced without
dodging and burning-in.

Another type of contrast control mask is a mask to increase
the contrast of a flat negative. This can be accomplished by
using the steps above to produce a contrast decrease mask and
then making a duplicate mask which would then give a positive
image. Sandwiched with the original negative, the mask can
really snap up an underexposed negative.

The reversal process can be eliminated by using Kodak
professional Duplicating film or Kodak LPD4 film. Sandwiched
with the negative, the contrast increase mask can help low-
density negative that would not otherwise produce very good
prints.
 

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2009