User's Manual

275
ADOBE PHOTOSHOP CS2
User Guide
Hue/Saturation command Adjusts the hue, saturation, and lightness values of the entire image or of individual
color components. See “The Hue/Saturation command” on page 295.
Match Color command Matches the color from one photo to another photo, from one layer to another layer, and
from a selection in an image to another selection in the same image or a different image. This command also adjusts
the luminance and color range and neutralizes color casts in an image. See “To match the color in different images”
on page 301.
Replace Color command Replaces specified colors in an image with new color values. See “To replace the color of
objects in an image” on page 304.
Selective Color command Adjusts the amount of process colors in individual color components. See “To use the
Selective Color command” on page 306.
Channel Mixer command Modifies a color channel and makes color adjustments not easily done with other color
adjustment tools. See “Mixing color channels” on page 304.
Tonal adjustment methods
There are several different ways to set an image’s tonal range:
• Drag sliders along the histogram in the Levels dialog box.
• Adjust the shape of the graph in the Curves dialog box. This method lets you adjust any point along a 0–255 tonal
scale and provides the greatest control over an image’s tonal quality.
• Assign target values to the highlight and shadow pixels using either the Levels or Curves dialog box. This can help
preserve important highlight and shadow details in images being sent to a printing press or laser printer. You
might also need to fine-tune the target values after sharpening.
• Adjust the tonality in the shadow and highlight areas using the Shadow/Highlight command. This adjustment is
especially useful for correcting photos in which strong backlighting silhouettes the subject or proximity to the
camera flash overlightens the subject slightly.
Viewing histograms and pixel values
About histograms
A histogram illustrates how pixels in an image are distributed by graphing the number of pixels at each color intensity
level. The histogram shows whether the image contains enough detail in the shadows (shown in the left part of the
histogram), midtones (shown in the middle), and highlights (shown in the right part) to make a good correction.
The histogram also gives a quick picture of the tonal range of the image, or the image key type. A low-key image has
detail concentrated in the shadows; a high-key image has detail concentrated in the highlights; and an average-key
image has detail concentrated in the midtones. An image with full tonal range has a number of pixels in all areas.
Identifying the tonal range helps determine appropriate tonal corrections.