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Chapter 1 Color Correction Basics 31
Gamma
Gamma refers to two different concepts. In a video signal, gamma refers to the
nonlinear representation of luminance in a picture displayed on a broadcast or
computer monitor. Since the eye has a nonlinear response to light (mentioned in
“The Y’C
B
C
R
Color Model” on page 24), applying a gamma adjustment while recording
an image maximizes the perceptible recorded detail in video signals with limited
bandwidth. Upon playback, a television or monitor applies an inverted gamma
function to return the image to its “original” state.
You want to avoid unplanned gamma adjustments when sending media from
Final Cut Pro to Color. It’s important to keep track of any possible gamma adjustments
that occur when exporting or importing clips in Final Cut Pro during the editing
process, so that these adjustments are accounted for and avoided during the
Final Cut Pro to Color round trip. For more information on gamma handling in
Final Cut Pro, see the Final Cut Pro User Manual.
Gamma is also used to describe a nonlinear adjustment made to the distribution of
midtones in an image. For example, a gamma adjustment leaves the black point and
the white point of an image alone, but either brightens or darkens the midtones
according to the type of adjustment being made. For more information on gamma and
midtones adjustments, see Chapter 9, “Primary In,” on page 163.
Chroma (Chrominance)
Chroma (also referred to as chrominance) describes the color channels in your shots,
ranging from the absence of color to the maximum levels of color that can be
represented. Specific chroma values can be described using two properties, hue and
saturation.
Hue
Hue describes the actual color itself, whether it’s red or green or yellow. Hue is
measured as an angle on a color wheel.