Primary Color Correction: Color Manipulation Tools - The Art and Technique of Digital Color Correction - page 134

Fig. 4.42 Flowerbench image and Avid Media Composer internal RGB Parade.
All of the black levels are elevated, but the red is the closest to being
down at 0IRE where it probably should be, followed closely by blue, and
the greens are highest of all. The red highlights appear to be clipped, and
they are as high as they can go. The greens highlights are low and so are
the blue highlights. Let's take care of those things first, then see what else
the image needs when we get those things taken care of.
Drag the bottom of the red curve to the right to pull down the shadows
in the red channel ( Figure 4.43 ). Watch the red cell of the RGB Parade
waveform until the lowest part of the shape gets to the bottom. Your
image will not look any better, but the tonal range of the red channel is
much improved. My correction pulled the 0 black level in red over to 24.
That means that everything that was between 24 and 0 on the original
image has now been pulled down to 0 on output.
Fig. 4.43