Primary Color Correction: Color Manipulation Tools - The Art and Technique of Digital Color Correction - page 152

that the dark grays are a little stretched out and the upper grays are a little
compressed. The red channel looks like nothing is really clipped or badly
crushed ( Figure 4.68 a ), but all of it is pretty dark compared to the green
channel. The blue channel really shows the clipping in the upper whites
( Figure 4.68 c ), just as I suspected it would, but notice that the chips from
the blacks up to the midtones match pretty well between the green chan-
nel and the blue channel. But nearly all of the upper gray chips are almost
the same luminance value in the blue channel. This explains why our
previous correction looks like it does.
Compare what the three channels are showing you visually against
the Tektronix RGB Parade waveform image.
In the RGB Parade waveform, in the upper left of Figure 4.69 , you can
see how compressed the chips above the midtone are in the blue chan-
nel. This effect is giving you more information, actually—it's just not so
visually simple to digest. The waveform is showing you that even though
the green channel image looked pretty good, it actually has quite a bit of
clipping going on in the upper grays.
Fixing these issues with Channels is a different matter than seeing
them, though. With Channels, the way to fix the problems is to combine
channels with each other. This is basically way too unintuitive for most
Fig. 4.69 Tektronix display of the “Chromadumonde_properex_cool” chart.