Specifications

ptg
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Introducing Color Correction
Using Manual Controls in Combination
with Automatic Controls
As mentioned, it’s usually best, and often necessary, to perform automatic
color correction in combination with manual color correction. This section
will cover a few of the most important manual controls that you’ll use to
modify automatic color corrections.
Manual luma controls
When you manipulate the dark, light, and midtone values of the luma sig-
nal, you actually are adjusting its setup, gain, and gamma, respectively.
Gain: When you correct the image’s lightest values, you are adjusting
the image’s white point, or gain. Increasing the gain value makes all light
values lighter. Decreasing the gain value makes all light values darker.
Gain adjustments are proportional, which means that all values increase
and decrease exponentially. In this way, gain adjustments “stretch” toward
white, with light values changing a lot and dark values changing a little.
Gamma: When you change the midtones (values between the darkest
and lightest values), you are adjusting the image’s luminance midpoint, or
gamma. Increasing the gamma value lightens the midtones and brings the
image closer to white. Decreasing the gamma value darkens the midtones
and brings the image closer to black.
Setup: When you correct the image’s darkest values, you are adjusting the
black point, or setup. Increasing the setup value makes all values lighter.
Decreasing the setup value makes all values darker. Setup adjustments are
additive, which means that all values increase and decrease by the same
amount. That said, you should typically use setup only to set your darkest
values to black.
These controls exist as sliders within the Color Correction tool.
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