Primary Color Correction: Color Control Primer - The Art and Technique of Digital Color Correction - page 91

Fig. 3.22 Standard zoom of the “grayscale_cool” image.
Fig. 3.23 Same image zoomed 2x in Color's internal vectorscope is called “50 percent zoom.”
foreground. Compare that to the “blue” image and you can see that
the vectorscope is favoring the blue and cyan vectors with almost no
yellow or green.
The key to many of these corrections is subtlety.