Primary Color Correction: Tonal Correction Tools - The Art and Technique of Digital Color Correction - page 54

Fig. 2.25 Curves interface for Synthetic Aperture's Color Finesse.
earlier, there are Curves tools in many different applications. If you prefer
to follow along in Color's Primary In room or in the Avid Curves tool or
one of the other applications, the process will be very similar.
The leftmost graph, which has a white diagonal line and is called Mas-
ter, gives you control over the overall signal—the composite of red, green,
and blue. The next three graphs to the right give you control over the
individual color channels: red, green, and blue, respectively. Each graph
has a diagonal colored line indicating the color channel it controls.
How Curves Work
The graphs are interactive. Clicking on a point in the graph and dragging it in a direction
alters the relationship between the incoming and outgoing levels. The incoming (source)
level is represented along the y axis (up and down) while the outgoing (corrected) signal
is represented along the x axis (side to side). So if we want to raise the black level, we
click on the point at the bottom left corner and raise it. To lower it, we click on the same
point and drag it straight to the right. This remaps the 0 value of the incoming signal,
basically saying “all of the values to the left of where I drag this point should be mapped
to 0.” If you drag the top right corner down, you remap what was 100 on the source
down to where you leave the point. If you drag the top right corner point to the left along