Primary Color Correction: Color Manipulation Tools - The Art and Technique of Digital Color Correction - page 118

After you've tried those moves, reset the shadow wheel to the default.
Practice trying to move specific combinations of cells with specific moves
of the wheels or trackballs:
• Moving toward green raises green while lowering red and blue
( Figure 4.13 ).
• Moving toward yellow raises red and green while lowering blue
( Figure 4.11 ).
• Moving toward red raises red while lowering blue and green
( Figure 4.21 ).
• Moving toward magenta raises red and blue while lowering green
( Figure 4.19 ).
• Moving toward blue raises blue while lowering red and yellow
( Figure 4.17 ).
• Moving toward cyan raises blue and green while lowering red
( Figure 4.15 ).
Another important trick to learn is this: if you want to maintain the
position of one cell while moving the other two, imagine a line drawn
from the color that you want to remain stationary across to the color
opposite it. For our example, we'll try to keep the green channel station-
ary while having the red and blue channels move up and down on either
side of it. So draw the imaginary line from green to magenta. To move red
and blue while maintaining the green cell's position, move the trackball
or wheel perpendicular to the imaginary line. For us, this perpendicular
line is from about 10 o'clock (raising red and lowering blue) to 4 o'clock
(raising blue and lowering red). This corresponds almost perfectly to the
“I” line on the vectorscope.
Thinking about what you are doing from a color theory perspective,
this makes sense. You are not moving toward or away from yellow at all.
You are maintaining the cursor's distance from green while moving it
toward yellow-red or blue-cyan.
Trying to maintain the position of the red channel while moving
green and blue in different directions means a move that corresponds
to the Q line of the vectorscope. This is approximately from 2 o'clock
(lowering green) to 8 o'clock (lowering blue). Let's make a short-
hand for these clock positions by dropping the quote marks and the
“o'clock.” For the next couple of paragraphs, numerical entries will
refer to clock positions around the color wheel or vectorscope. (Techni-
cally it would be best to use degrees, but clock positions are easier, I think.)
Trying to maintain the position of the blue channel while moving
green and red in different directions means a move from 1 (lowering
green) to 7 (lowering red).
If you are not following along with the tutorial in an application
right now, you may need some visual support. Here are some examples.