Operation Manual

2 In the Levels area of the Adjustments inspector or the Adjustments pane of the Inspector
HUD, choose Luminance from the Channel pop-up menu, then click the Auto Levels
Combined button.
Click the Auto Levels Combined
button to automatically set the
levels for the image based on the
combined luminance of all three
color channels.
The levels of the image are automatically adjusted. To fine-tune the Levels adjustment,
see Adjusting the Luminance Levels in an Image.
Using the Auto Levels Separate Button to Adjust RGB Channels
Individually
When you want to automatically adjust the levels of an image based on individual
evaluations of the red, green, and blue channels, you use the Auto Levels Separate button
in the Levels adjustment. Red, green, and blue channels are adjusted based on the
evaluation of each channel. You use the Auto Levels Separate button when you want to
correct the color cast in the image in addition to correcting the contrast.
Before Auto Levels Separate
adjustment
After Auto Levels Separate
adjustment
556 Chapter 17 Making Image Adjustments