Primary Color Correction: Color Manipulation Tools - The Art and Technique of Digital Color Correction - page 124

certain colors, then we need to use saturation to bring those levels in to
the correct range. Also, corrections such as raising the blacks or stretching
gamma can increase saturation and cause color noise in various portions
of the picture. Using the high or low saturation controls can help diminish
the appearance of noise in these areas.
One of the other important reasons for adjusting saturation is in
matching shots. If you are trying to match shots that were white balanced
differently, adjusting saturation in certain tonal ranges after balancing the
colors will often help tweak the match in a way that simply balancing the
colors cannot do.
The other important reason for adjusting saturation is in creating a
look. So many of the great looks that the colorists developed for the later
chapters of this topic relied on the creative use of saturation. Usually this
meant lowering the saturation, but sometimes it meant taking saturation
to the extreme upper limits.
Saturation adjustments are also important when you're trying to take
an image in a very different color direction than it was intended to have.
The reason for this is that if you are trying to introduce a totally new color
scheme to an image, the old colors must be nulled out so that they don't
“pollute” the colors you're trying to add. For example, if you are trying
to create an icy-blue skin tone on a person with a normal skin tone, the
reds and yellows of that skin tone will blend in with the correction you're
trying to make. If you first lower the saturation in the areas of that skin
tone, or across the entire image, you will find that your icy-blue look will
be much easier to achieve and much more satisfactory in the end.
Obviously, one of the important reasons to adjust saturation is sim-
ply “to make it look good.” Saturation levels are very subjective—like
gamma levels. When you're doing primary color correction, you some-
times “break” something that needs to be fixed elsewhere. That is often
the case with saturation. If you had to add warmth to the midtones of an
image in order to get a nice healthy skin tone, it's possible that other areas
of your midtones will need to have saturation reduced. Or possibly the
addition of warmth in the midtones meant that some cool element in the
midtones became desaturated, so you may be able to bring the saturation
up in that case, though the only real way to fight this would probably be
a secondary color correction, which we will discuss in the next chapter.
Histograms
Most histograms used in color correction applications are just tools for
analysis ( Figures 4.22 and 4.23 ) , but there are some that allow you to
actually manipulate the image with the histogram interface. Color Finesse
actually gives you both. As part of their analytical tools, along with RGB
Parade waveforms and vectorscopes, Color Finesse offers up a histogram for