Apple Final Cut Pro 7 - Manual (Page 1306)

Learning to Read the Waveform Monitor
The Waveform Monitor shows you the relative levels of luma and chroma saturation in
the clip currently being examined. These values are displayed from left to right, mirroring
the relative distribution of these levels from the left to the right of the image in the frame.
Spikes and dips in the displayed waveforms correspond to hot spots and dark areas in
your picture.
This dip in the waveform
matches the position of
the dog.
1306 Chapter 78 Measuring and Setting Video Levels