Primary Color Correction: Tonal Correction Tools - The Art and Technique of Digital Color Correction - page 44

Each group—consisting of a circular color wheel (sometimes referred
to as hue offset wheels ) and three vertical bars—controls one of the three
tonal ranges. The far left group is for shadows. The middle group is for
midtones or gamma. And the right group is for highlights.
If you have an Avid Artist Color controller, a JLCooper MCS Spectrum
controller or Eclipse-CX, or a Tangent Devices Element, Wave ( Figure
2.11 ), CP100, or CP200-BK controller, the dials and trackballs on the con-
troller are linked to the various controls on the GUI. For most controllers,
each trackball controls the corresponding Hue Offset wheel on the GUI.
The rings around each trackball control the black point, gamma distribu-
tion, and white point (from left to right). And the dials at the top of the
device control saturation. On all of these devices, the dials, buttons, and
knobs are customizable and serve several functions, depending on the
way it is customized by the user or by “the factory.”
If you are using Color with just a mouse or a trackball, you can bring the
shadows or blacks up or down by dragging the small, horizontal cyan line
that is at the bottom of the black/white bar on the left. There is a similar small,
horizontal cyan line across the middle of the middle black/white bar. Drag
this up or down to control the midtones of your image. To control highlights,
drag the cyan line at the top of the righthand black/white bar up or down.
The second way to control tonal corrections is to use the entry windows
for master lift, master gamma, and master gain controls along the right side
of the screen, near the top. You can type in numbers, but that is hardly intui-
tive. The best way to control these sliders with a mouse is to use the scroll
wheel. Hover the mouse over the numeric lift, gamma, or gain number,
click down on the scroll wheel, and drag the mouse left and right to adjust in
gross increments, or scroll the wheel itself up and down for fine increments.
The default tab in this location is the Basic tab, but you can also make
corrections with the Advanced tab. We'll get into that a little more in

D e f i n i t i o n
hue offset wheels: A
circular user interface pat-
terned like a color wheel
or vectorscope that allows
for the control of both hue
and saturation. Hue values
are indicated around the
perimeter of the circle and
saturation is indicated by
the respective distance
from the center of the
circle. With some color cor-
rectors with manual user
interfaces, these hue offset
wheels can be controlled
by multiple trackballs. Each
wheel controls a different
tonal range.

gamma: Gamma has
several definitions, but the
primary one that is used
by colorists is to describe
the midtones or midrange
tones of a picture. Gamma
can also refer to the curve
or steepness of the transi-
tion from black to white.
These are similar defini-
tions in a way, because by
altering the gamma—or
midrange—of a picture,
the curve or transition
from shadow to highlight
is also affected. Directors
of Photography usually
refer to gamma to mean
the response curve from
black to white instead of
meaning the midtones,
specifically.

Fig. 2.11 The Tangent
Devices Wave control
surface is compatible with
Apple Color and several
other color correction
applications.