Brightness Units
To lower the measured density and move the curve down, decrease the
brightness number for a channel. To raise density, raise the brightness
number (see Figure 6.3).
The numbers used to measure brightness values are arbitrary units
that represent beam intensities for each of the three channels. For ex-
ample, the red brightness value represents the red beam intensity. Pos-
sible brightness values might be the following:
Red: 69 Green: 82 Blue: 64
Because the values are arbitrary units, they are relative measure-
ments. They do not represent the measured brightness of the beam or
the measured density of the film.
For example, if the current brightness value is 55 and you change it to
45, the response curve will shift downward. Exactly how much the
curve shifts depends on the film, processing, and other values. Be-
cause the effects of changes cannot be predicted exactly, color balanc-
ing requires running many tests in a process of trial and error.
Note: Brightness and contrast calibration errors
may occur if the values selected exceed the CRT in-
ternal calibration range. Generally, this occurs
when brightness values are decreased by more
than 20 units for any channel. Try increasing the
repeats value as described later in this chapter. To
recover from a calibration error, see Chapter 7.
Color Balance • 6-7
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