User's Manual

310

ADOBE PHOTOSHOP CS2

User Guide

Auto Color Correction Options dialog box

A. Auto Contrast option B. Auto Levels option C. Auto Color option D. Set target colors, black point, and white point

1 Click the Options button in the Levels dialog box or Curves dialog box.

2 Specify the algorithm you want Photoshop to use to adjust the overall tonal range of an image:

Enhance Monochromatic Contrast Clips all channels identically. This preserves the overall color relationship while

making highlights appear lighter and shadows appear darker. The Auto Contrast command uses this algorithm.

Enhance Per Channel Contrast Maximizes the tonal range in each channel to produce a more dramatic correction.

Because each channel is adjusted individually, Enhance Per Channel Contrast may remove or introduce color casts.

The Auto Levels command uses this algorithm.

Find Dark & Light Colors Finds the average lightest and darkest pixels in an image and uses them to maximize

contrast while minimizing clipping. The Auto Color command uses this algorithm.

3 Select Snap Neutral Midtones if you want Photoshop to find an average nearly neutral color in an image and then

adjust the gamma (midtone) values to make the color neutral. The Auto Color command uses this algorithm.

4 To specify how much to clip black and white pixels, enter percentages in the Clip text boxes. A value between 0.0%

and 1% is recommended.

By default, Photoshop clips the black and white pixels by 0.1%—that is, it ignores the first 0.1% of either extreme

hen identifying the lightest and darkest pixels in the image. Because of the better output quality of today’s scanners

and digital cameras, these default clipping percentages may be too high.

5 To assign (target) color values to the darkest, neutral, and lightest areas of an image, click a color swatch.

6 Do one of the following:

• To use the settings in the current Levels or Curves dialog box, click OK. If you subsequently click the Auto button,

Photoshop reapplies the same settings to the image.

• To save the settings as the default, select Save as Defaults, and then click OK. The next time you open the Levels

or Curves dialog box, you can apply the same setting by clicking the Auto button. The default clipping percentages

are also used by the Auto Level, Auto Contrast, and Auto Color commands.

Note: W

hen you save the Auto Color Correction options as defaults for Auto Color, Auto Levels, and Auto Contrast, it

does not matter what algorithm you select in step 2. The three auto-correction commands use only those values that you

set for the target colors and clipping. The only exception is that the Auto Color command also uses the Snap Neutral

Midtones option.