Apple Color 1.0 - Manual (Page 192)

192 Chapter 9 Primary In
Curves in Color are edited using B-Splines, which use control points that aren’t actually
attached to the curve control to “pull” the curve into different shapes, like a strong
magnet pulling thin wire. For example, here’s a curve with a single control point that’s
raising the highlights disproportionately to the midtones:
The control point hovering above the curve is pulling the entire curve upward, while
the ends of the curve are pinned in place.
The complexity of a curve is defined by how many control points are exerting influence
on the curve. If two control points are added to either side, and moved down, the
curve can be modified as seen below.
To make curves sharper, move their control points closer together. To make curves
more gentle, move the control points farther away from one another.
The following procedures describe how to create, remove, and adjust the control points
that edit curve controls.
To add control points to a curve:
m Click anywhere on the curve itself.
To adjust a control point:
m Drag it anywhere within the curve control area.