Operation Manual

3 Once the white clipping point is adjusted, click either the Auto Levels Combined or the
Auto Levels Separate button in the Levels area of the Adjustments inspector or the
Adjustments pane of the Inspector HUD to view the effect on the image.
Adjusting the Luminance Levels in an Image
When you want to adjust the overall tonality of an image, you use the Levels adjustment
controls based on a histogram that shows luminance. When the histogram is set to show
luminance, it displays the cumulative brightness values for all three color channels for
each pixel. You use the histogram’s luminance view when you want to adjust an image’s
tonal values without affecting the color cast.
Before Levels adjustment After Levels adjustment
To adjust levels in an image based on luminance
1 Select an image.
2 By default, the Levels histogram is off. Turn it on by selecting the Levels checkbox in the
Levels area of the Adjustments inspector or the Adjustments pane of the Inspector HUD.
The Levels histogram appears.
White Levels slider
Black Levels slider
3 Choose Luminance from the Channel pop-up menu.
559Chapter 17 Making Image Adjustments