Apple Color 1.5 - Manual (Page 196)

Spotting Color Casts with the Vectorscope
You can also use the Vectorscope to spot whether there’s a color cast affecting portions
of the picture that should be neutral (or desaturated). Crosshairs in the Vectorscope
graticule indicate its center. Since desaturated areas of the picture should be perfectly
centered, an off-center Vectorscope graph representing an image that has portions of
white, gray, or black clearly indicates a color imbalance.
The Color Targets
The color targets in the Vectorscope line up with the traces made by the standard color
bar test pattern, and can be used to check the accuracy of a captured video signal that
has recorded color bars at the head.
These targets also correspond to the angles of hue in the color wheels surrounding the
Color Balance controls in the Primary In and Out and Secondaries rooms. If the hues of
two shots you’re trying to match don’t match, the direction and distance of their offset
on the Vectorscope scale give you an indication of which direction to move the balance
control indicator to correct for this.
At a zoom percentage of 75 percent, the color targets in the Vectorscope are calibrated
to line up for 75 percent color bars. Zooming out to 100 percent calibrates the color
targets to 100 percent color bars. All color is converted by Color to RGB using the Rec.
709 standard prior to analysis, so color bars from both NTSC and PAL source video will
hit the same targets.
Note: If Broadcast Safe is turned on, color bars’ plots may not align perfectly with these
targets.
196 Chapter 8 Analyzing Signals Using the Video Scopes