PDF (adobe.com)

Vectorscope

The Vectorscope displays a circular chart, similar to a color wheel, that shows the video’s chrominance information. Saturation is measured from the center of the chart outward. Saturated, vivid colors produce a pattern some distance from the center of the chart, while a black‑and‑white image produces only a dot at the center of the chart. The particular color, or hue, of the image determines the direction (angle of the pattern). Small target boxes  indicate where fully saturated magenta, blue, cyan, green, yellow, and red (present in a color bars test pattern) should appear. In NTSC video, chrominance levels should not exceed these target areas.

Vectorscope

A.
Target boxes

B.
Image profile

The Vectorscope has the following controls:

Intensity
Adjusts the brightness of the pattern display. It does not affect the video output signal.

75%
Default position. Use to check video input in which standard 75% intensity bars, like those in Adobe Premiere Pro, are used.

100%
Shows the entire range of video signal chrominance. Use with video input containing 100% intensity bars.