Apple Color 1.5 - Manual (Page 230)

• If Limit Shadow Adjustments is turned on: A linear falloff is applied to color adjustments
made with the Shadow control such that black receives 100 percent of the adjustment
and white receives 0 percent of the adjustment. This is the method to use if you want
to be able to selectively correct shadows while leaving highlights untouched.
Note: To better illustrate the effect of the Shadow color control, the previous examples
were shown with Broadcast Safe turned off so that image values below 0 percent wouldn't
be clipped.
Midtones Color Adjustments
Adjustments made with the Midtone color balance control apply the correction using a
power operation (the new pixel value = old pixel value ^ adjustment). The result is that
midtones adjustments have the greatest effect on color values at 50 percent lightness
and fall off as color values near 0 and 100 percent lightness.
230 Chapter 9 The Primary In Room