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.
- Do one of the following:
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.
- In the Properties panel (CC, CS6) or Adjustments panel
(CS5), Alt-click (Windows) or Option-click (Mac OS) the Auto button.
- Under Algorithms in the Auto Color Correction Options
dialog box, select the Enhance Monochromatic Contrast option.
- Specify the shadows and highlights that are clipped,
and adjust the target color for the midtones.
- 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.
- Do one of the following:
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.
- In the Properties panel (CC, CS6) or Adjustments panel
(CS5), Alt-click (Windows) or Option-click (Mac OS) the Auto button.
- Under Algorithms in the Auto Color Correction Options
dialog box, select the Find Dark & Light colors option.
- Select the Snap Neutral Midtones option.
- Specify the shadows and highlights that are clipped,
and adjust the target color for the midtones.
- 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.
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
- Click the Levels or Curves icon in the Adjustments
panel.
- Alt-click (Windows) or Option-click (Mac OS) the Auto
button in the Properties panel (CC, CS6) or Adjustments panel (CS5).
- 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.
- 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.
- 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.
- To assign (target) color values to the darkest, neutral,
and lightest areas of an image, click a color swatch.
- 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 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.
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.
- (Optional) Select an area of the image to equalize.
- Choose Image > Adjustments >
Equalize.
- 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.
- Do one of the following:
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.
- In the Properties panel (CC, CS6) or Adjustments panel
(CS5), Alt-click (Windows) or Option-click (Mac OS) the Auto button.
- Under Algorithms in the Auto Color Correction Options
dialog box, select Enhance Per Channel Contrast.
- Adjust the amount of shadow and highlight values that
are clipped, and adjust the target color for the midtones.
- Click OK to apply the Auto option settings.
More Help topics
Adjusting image color and tone
