2011

To uniformly modify the levels on all channels or on a single channel of an
image:
1 From the Tools tab, drag a Photo Lab tool from the Color Correction
folder to the dependency graph in the Schematic view.
2 Select exposure and contrast units.
3 Set Printer Lights per F-stop by dragging the field to the right or to the
left.
4 Do one of the following:
■ Drag any of the red (R), green (G), or blue (B) channel fields to the
right to increase or to the left to decrease levels uniformly on all three
channels. Alternatively you can also drag the overall luminance (L)
field to achieve the same result.
■ Enter a value into any channel's field and press Enter.
■ Select a single channel that you want to modify by deselecting Lock,
then drag the channel field to the right to increase, or to the left to
decrease, the values of the channel. You may also enter a value into
any channel's field and press Enter.
The other two channel fields and the overall luminance field update
to reflect the change.
Using the Trackball to Modify the Levels of an Image
The trackball allows you to modify values with a more freestyle, intuitive
approach. The trackball emulates a typical 360-degree color wheel that can
be dynamically changed by dragging the center of the color wheel.
Consequently, the effect on the red, blue, and green channels is predictable.
For example, dragging the trackball towards the red portion of the color wheel
increases the value of the red channel, but decreases the values of both the
blue and green channels, and adds blue and green to the shadows and
midtones of the image.
Modifications made using the trackball are cumulative; each movement of
the trackball is added to the previous one. The trackball changes color to reflect
the degree of change.
648 | Chapter 26 Color Correction