EVALUATION AND INTERPRETATION
a. Use the densitometer to perform several density readings and to determine
the amount of density on the strip. Do not read the margins of the film.
b. Ensure that the densitometer is properly calibrated.
c. Zero the densitometer.
d. Select four unexposed areas on the film; check for fogging.
The term "base-plus-fog" is used to describe the density on this unexposed
e. Measure the density in four unexposed areas. Add all four densities and
divide by four to get the average density.
f. Record the average base-plus-fog density on the film.
g. Plot this number on the appropriate area of the chart (gross fog).
h. Select step on sensitometric strip and measure approximately 1.0 to 1.3
i. Read the density on the opposite side of the sensitometric strip at the same
(1) If one on side step five has 1.0 density, read the density on step five of
the opposite side of the film.
(2) If the density differs, average the density values. This determines the
"speed" of the film.
Mark the measurement of density on the film.
Remember paragraph 7-5 step i(2) that was used to determine the "speed."
This step will be used as a reference point for each day's sensitometric strip.
k. Plot the density reading on the appropriate area of the chart.
l. Use four steps darker if the speed has 21 steps. Use two steps darker if the
speed has 11 steps.
Remember to read both sides of the film and average the density values.