Just for Color: Hue/Saturation

Just for Color: Hue/Saturation

The third of three essential color correction tools in After
Effects is Hue/Saturation. This one has many individualized
uses:
. Desaturating an image or adding saturation (the tool’s
most common use)
. Colorizing images that were created as grayscale or
monochrome
. Shifting the overall hue of an image
. De-emphasizing, or knocking out completely, an individual
color channel
All of these uses recur in Chapters 12 through 14 to create
monochrome elements, such as smoke, from scratch.
The Hue/Saturation control allows you to do something
you can’t do with Levels or Curves, which is to directly
control the hue, saturation, and brightness of an image.
The HSB color model is merely an alternate slice of RGB
color data. All real color pickers, including the Apple and
Adobe pickers, handle RGB and HSB as two separate but
interrelated modes that use three values to describe any
given color.
In other words, you could arrive at the same color adjustments
using Levels and Curves, but Hue/Saturation gives
you direct access to a couple of key color attributes that
are otherwise diffi cult to get at. To desaturate an image is
essentially to bring the red, green, and blue values closer
together, reducing the relative intensity of the strongest
of them; a saturation control lets you do this in one step,
without guessing.

Often is the case where colors are balanced but merely too
“juicy” (not a strictly technical term, but one that may make
sense in this context), and lowering the Saturation value
somewhere between 5 and 20 can be a direct and effective
way to pull an image adjustment together (Figure 5.22).
It’s essential to understand the delivery medium as well,
because fi lm is more tolerant and friendly to saturated
images than television.

The other quick fi x that Hue/Saturation affords you is a
shift to the hue of the overall image or of one or more of
its individual channels. The Channel Control menu for
Hue/Saturation includes not only the red, green, and
blue channels but also their chromatic opposites of cyan,
magenta, and yellow. When you’re working in RGB color,
these secondary colors are in direct opposition, so that, for
example, lowering blue gamma effectively raises the yellow
gamma, and vice versa.
The HSB model includes all six individual channels,
which means that if a given channel is too bright or oversaturated,
you can dial back its Brightness & Saturation
levels, or you can shift Hue toward a different part of the
spectrum without unduly affecting the other primary and
secondary colors. This can even be an effective way to
reduce blue or green spill