Adobe Photoshop CS4 - Manual (Page 175)

168 USING PHOTOSHOP CS4
Color and tonal adjustments
Last updated 1/10/2010
Curves overview
You can use Curves or Levels to adjust the entire tonal range of an image. The Curves adjustment lets you adjust points
throughout the tonal range of an image (from shadows to highlights). Levels have only three adjustments (white point,
black point, gamma). You can also use Curves to make precise adjustments to individual color channels in an image.
You can save Curves adjustment settings as presets. See “
Save adjustment settings ” on page 163 and “ Reapply
adjustment settings ” on page 163.
Curves options
A. Sample in image to set black point. B. Sample in image to set gray point. C. Sample in image to set white point. D. Edit points to modify
the curve. E. Draw to modify the curve. F. Curves type drop-down menu. G. Set black point. H. Set gray point. I. Set white point. J. Show
clipping.
In the Curves adjustment, the tonal range is represented as a straight diagonal baseline, because the input levels (the
original intensity values of the pixels) and output levels (new color values) are identical.
Note: After you’ve made an adjustment to the tonal range of a curve, Photoshop continues to display the baseline as a
reference. To hide the baseline, turn off Show Baseline in the Curve Display Options.
The horizontal axis of the graph represents the input levels; the vertical axis represents the output levels.
Default Curves settings for CMYK and RGB images
A. Default orientation of CMYK tonal output bar B. CMYK Input and Output values in percentages C. Default orientation of CMYK tonal
input bar D. Default orientation of RGB tonal output bar E. RGB Input and Output values in intensity levels F. Default orientation of RGB
tonal input bar
A
G
F
H
I
J
B
C
D
E
A B C D E F