Apple Color 1.0 - Manual (Page 197)

Chapter 9 Primary In 197
3 Add a control point below the first control point you created, and drag it up until the
man’s face lightens.
The man’s face is now brighter, but the shadows are now a bit washed out.
4 Add one last control point underneath the last control point you created, and drag it
down just a little bit to deepen the shadows, without affecting the brighter portions of
the image.
As you can see, the Luma curve is a powerful tool for making extremely specific
changes.
Using Curves to Adjust Color
Unlike the color balance controls, which adjust all three color channels simultaneously,
each of the color curve controls affects a single color channel. Additionally, the red,
green, and blue color curves let you make adjustments within specific areas of tonality
defined by the control points you add to the curve. This means that you can make very
exact color adjustments that affect regions of the image that are as narrow or broad as
you define.
The Luma Curve Limits the Range of the Primary Contrast Sliders
One important aspect of the curve controls is that they can limit the range of
subsequent adjustments with the primary contrast sliders in the same room. This can
be clearly seen when you make an adjustment to lower the white point of the image
using the Luma curve. Afterward, you’ll find yourself unable to use the Highlight
contrast slider to raise the image brightness above the level that’s set by the Luma
curve. You can still make additional contrast adjustments in other rooms.