Control strips and reference strips
Processing records of mechanical and
Since the details of the monitoring procedure
change with each color process, process-monitoring
manuals, such as Kodaks Z-series, are necessary
supplements to a color process-monitoring system.
The monitoring manuals describe the process, the
specific control strip to use, the steps to read, the
calculation of reference values and control values, the
specific plot patterns, and the plot-pattern
Control strips for color process monitoring are
supplied by the manufacturer of the color
light-sensitive material or process. The most common
control strips used in Navy imaging facilities are
Kodak process-control strips. Like black-and-white
control strips, color control strips have a series of
neutral-density steps. Process monitoring relies
primarily on the measurement of densities of the steps.
It is important to measure the minimum density
and, usually, two steps representing intermediate
tones. Monitoring D-max is also desirable for color
reversal film and paper. The relationship among the
three color measurements of a step is used to monitor
color balance. The difference in the readings from the
two steps (HD-LD) provides measurements of red,
green, and blue contrast.
Control strips must be stored at 0°F (-18°C) or
lower to minimize color shifts. The strips are
stabilized and given an expiration date, so they
provide a reliable tool to monitor processes. The
strips should be removed from the freezer, one at a
time, as they are needed.
A number of control strips from each control-strip
batch are processed by the manufacturer. One of the
processed strips is included with each package of
control strips. These processed strips are called
reference strips. The reference strips provide a means
for imaging facilities to determine a process standard
in terms of densitometer readings.
By reading these reference strips and applying
correction factors (supplied with the control strips) to
specified steps, you can determine the initial reference,
mean, or aim values.
The first time color process monitoring is used or
the first time a process is started up, the steps for
establishing a process-monitoring system are as
1. Ensure that chemical and mechanical
specifications are met. These include mixing
procedures, processing temperatures, times, and so
2. Determine initial reference values for the
particular code of control strips you are using. This
generally consists of reading the reference strip on the
densitometer, recording the densities, and adding or
subtracting correction factors (supplied with control
strips). (See fig. 2-16.) When available, average the
reading of several reference strips to minimize the
effects of variability.
NOTE: Be sure that the reference strips and
control strips you are using have the same code
number. A code number is assigned to each emulsion
batch, and this code number changes with each
emulsion batch manufactured.
3. Process five control strips, one in different
production runs. You should always feed the strip in
a continuous processor with the low-density end first.
The end of the film with the low-density steps is
indicated with a dimple on the film. You should also
feed the control strips into the processor at the same
location of the feed tray. It does not matter whether
you feed from the center, the far-right side, or the
far-left side. It is important for you to process the
control strips consistently to reduce variability.
4. Read the red, green, and blue densities of
the specified control-strip density steps on the
densitometer and average the values.