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154 Chapter 8 Video Scopes
How the color targets in the Vectorscope relate to the saturation of the Vectorscope
graph depends on the scale the Vectorscope is set to:
 If the Vectorscope scale is set to 75 percent, then 75 percent color bars will hit the
targets.
 If the Vectorscope scale is set to 100 percent, then 100 percent color bars will hit the
targets.
Note: All color is converted by Color to RGB using the Rec. 709 standard prior to
analysis. As a result, color bars from both NTSC and PAL source video will hit the same
targets.
The I Bar
The –I bar shows the proper angle at which the hue of the dark blue box in the color
bars test pattern should appear. This dark blue box, which is located to the left of the
100-percent white reference square, is referred to as the Inphase signal, or I for short.
The I bar (positive I bar) overlay in the Vectorscope is also identical to the skin tone line
in Final Cut Pro. It’s helpful for identifying and correcting the skin tones of actors in a
shot. When recorded to videotape and measured on a Vectorscope, the hues of human
skin tones, regardless of complexion, fall along a fairly narrow range (although the
saturation and brightness vary). When there’s an actor in a shot, you’ll know whether or
not the skin tones are reproduced accurately by checking to see if there’s an area of
color that falls loosely around the I bar.
If the skin tones of your actors are noticeably off, the offset between the most likely
nearby area of color on the Vectorscope and the skin tone target will give you an idea
of the type of correction you should make.