Apply the Auto Contrast adjustment

The Auto Contrast command adjusts image contrast automatically. Because Auto Contrast does not adjust channels individually, it does not introduce or remove color casts. It clips the shadow and highlight values in an image and then maps the remaining lightest and darkest pixels in the image to pure white (level 255) and pure black (level 0). This makes the highlights appear lighter and shadows appear darker.

By default, when identifying the lightest and darkest pixels in an image, Auto Contrast clips the white and black pixels by 0.5%—that is, it ignores the first 0.5% of either extreme. You can change this default using the Auto Color Correction Options found in the Levels and the Curves dialog boxes.

Auto Contrast can improve the appearance of many photographic or continuous-tone images. It does not improve flat‑color images.

  1. Do one of the following:
    • Click the Levels or Curves icon in the Adjustments panel.

    • Choose Layer > New Adjustment Layer and choose either Levels or Curves. Click OK in the New Layer dialog box.

    Note:

    You can also choose Image > Auto Contrast to apply the adjustment directly to the image layer. Keep in mind that this method discards image information and its application is automatic. You cannot adjust any of the options in the following steps.

  2. In the Properties panel, Alt-click (Windows) or Option-click (Mac OS) the Auto button.

  3. Under Algorithms in the Auto Color Correction Options dialog box, select the Enhance Monochromatic Contrast option.
  4. Specify the shadows and highlights that are clipped, and adjust the target color for the midtones.
  5. Click OK to apply Auto Contrast.

Remove a color cast using Auto Color

Auto Color adjusts the contrast and color of an image by searching the image to identify shadows, midtones, and highlights. By default, Auto Color neutralizes the midtones using a target color of RGB 128 gray and clips the shadows and highlight pixels by 0.5%. You can change these defaults in the Auto Color Correction Options dialog box.

  1. Do one of the following:
    • Click the Levels or Curves icon in the Adjustments panel.

    • Choose Layer > New Adjustment Layer and choose either Levels or Curves. Click OK in the New Layer dialog box.

    Note:

    You can also choose Image > Auto Color to apply the adjustment directly to the image layer. Keep in mind that this method discards image information and is automatic. You cannot adjust any of the options in the following steps.

  2. In the Properties panel, Alt-click (Windows) or Option-click (Mac OS) the Auto button.

  3. Under Algorithms in the Auto Color Correction Options dialog box, select the Find Dark & Light colors option.
  4. Select the Snap Neutral Midtones option.
  5. Specify the shadows and highlights that are clipped, and adjust the target color for the midtones.
  6. Click OK to apply Auto Color.

Set Auto adjustment options

The Auto Color Correction options control the automatic tone and color corrections available in both Levels and Curves. It also controls the settings for the Auto Tone, Auto Contrast, and Auto Color commands. The Auto Color Correction options let you specify shadow and highlight clipping percentages, and assign color values to shadows, midtones, and highlights.

You can apply the settings during a single use of the Levels or Curves adjustment, or you can save the settings as default values when applying Auto Tone, Auto Contrast, Auto Color, and the Auto option for Levels and Curves.

Photoshop Auto Color Correction options
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 Levels or Curves icon in the Adjustments panel.
  2. Alt-click (Windows) or Option-click (Mac OS) the Auto button in the Properties panel.

  3. 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 Tone 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.

  4. 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.
  5. 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 when identifying the lightest and darkest pixels in the image. Because of the better output quality of modern scanners and digital cameras, these default clipping percentages might be too high.

  6. To assign (target) color values to the darkest, neutral, and lightest areas of an image, click a color swatch.
  7. Do one of the following:
    • To use the settings in the current Levels or Curves adjustment, click OK. If you then 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 access Levels or Curves in the Adjustments panel, you can apply the same setting by clicking the Auto button. The Auto Tone, Auto Contrast, and Auto Color commands also use the default clipping percentages.

    Note:

    When you save the Auto Color Correction options as defaults for Auto Color, Auto Tone, and Auto Contrast, it does not matter what algorithm you select in step 3. 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.

Video tutorial: Auto corrections

Video tutorial: Auto corrections
Corey Barker

Using the Equalize command

The Equalize command redistributes the brightness values of the pixels in an image so that they more evenly represent the entire range of brightness levels. Equalize remaps pixel values in the composite image so that the brightest value represents white, the darkest value represents black, and intermediate values are evenly distributed throughout the grayscale.

You can use the Equalize command when a scanned image appears darker than the original and you want to balance the values to produce a lighter image. Using Equalize together with the Histogram panel lets you see before-and-after brightness comparisons.

Keep in mind that the Equalize command applies adjustments directly to the image layer and deletes image information. For nondestructive adjustments, use adjustment layers or edit in Adobe Camera Raw.

  1. (Optional) Select an area of the image to equalize.
  2. Choose Image > Adjustments > Equalize.
  3. If you selected an area of the image, select what to equalize in the dialog box, and click OK:

    Equalize Selected Area Only

    Evenly distributes only the pixels in the selection.

    Equalize Entire Image Based On Selected Area

    Evenly distributes all image layers based on those in the selection.

Adjust black and white points with the Auto option

The Auto option for Levels and Curves and the Auto Tone command automatically adjust the black point and white point in an image. This clips a portion of the shadows and highlights in each channel and maps the lightest and darkest pixels in each color channel to pure white (level 255) and pure black (level 0). The intermediate pixel values are redistributed proportionately. As a result, using the Auto option or Auto Tone increases the contrast in an image because the pixel values are expanded. Because the Auto option and Auto Tone adjust each color channel individually, it may remove color or introduce color casts.

The Auto option and Auto Tone give good results in certain images with an average distribution of pixel values that need a simple increase in contrast.

By default, the Auto option and the Auto Tone command clip the white and black pixels by 0.1%—that is, it ignores the first 0.1% of either extreme when identifying the lightest and darkest pixels in the image. The default settings for the Auto option can be changed in the Auto Color Correction Options dialog box.

  1. Do one of the following:
    • Click the Levels or Curves icon in the Adjustments panel.

    • Choose Layer > New Adjustment Layer and choose either Levels or Curves. Click OK in the New Layer dialog box.

    Note:

    You can choose Image > Auto Tone to apply the adjustment directly to the image layer. Keep in mind that this method discards image information and is automatic. You cannot adjust any of the options in the following steps.

  2. In the Properties panel, Alt-click (Windows) or Option-click (Mac OS) the Auto button.

  3. Under Algorithms in the Auto Color Correction Options dialog box, select Enhance Per Channel Contrast.
  4. Adjust the amount of shadow and highlight values that are clipped, and adjust the target color for the midtones.
  5. Click OK to apply the Auto option settings.

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