3.4

Chapter 16 Making Image Adjustments 353
3 In the Curves area of the Adjustments inspector or the Adjustments pane of the Inspector HUD,
click the Auto Curves Separate button.
Click the Auto Curves
Separate button to
automatically set
the tonal curve for
the photo based
on an evaluation of
each color channel’s
luminance values.
The tonal curve of the image is automatically adjusted for each color channel. To ne-tune the
tonal curve adjustment, see Adjusting the Tonal Curve of an Image Using the Curves Controls on
page 353.
Adjusting the Tonal Curve of an Image Using the Curves Controls
You use the tonal curve in the Curves adjustment controls to adjust the overall tonality of an
image. There are two types of tonal curve adjustments: RGB and Luminance. When you want
to specify a tonal curve adjustment that modies both the contrast and the tint in the image,
you use the RGB tonal curve. When you want to adjust the overall tonality of an image without
aecting its color cast, you use the luminance tonal curve.
As you perform a tonal curve adjustment, a histogram is displayed behind the tonal curve and
is updated as you manipulate the tonal curve. You can specify the tonal range of the histogram
to focus the graph on the part of the tonal curve you plan to work with. For example, if you plan
to manipulate the contrast in the shadow areas of the image, you can limit the tonal range of
the tonal curve and histogram to display pure black to 50 percent gray only. You can also extend
the range of the histogram and tonal curve beyond pure white to capture highlight detail that
would be clipped otherwise.
You can also adjust the tonal curve of each color channel independently. For more information,
see Using the Curves Controls for Color Correction on page 361.
Before Curves adjustment After Curves adjustment