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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 and Reapply adjustment settings.

Curves dialog box

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 in the Curves dialog box, Photoshop continues to display the baseline as a reference. To hide the baseline, turn off Show Baseline in the Curve Grid Options.
The horizontal axis of the graph represents the input levels; the vertical axis represents the output levels.
Default Curves dialog boxes 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

Set Curve display options

You can control the curve grid display using the Curve display options.

  1. Do one of the following:

    • Click the Curves icon  or a Curves preset in the Adjustments panel, or choose Curves from the panel menu.

    • Choose Layer > New Adjustment Layer > Curves. Click OK in the New Layer dialog box.

    • Choose Image > Adjustments > Curves.

    Note: Choosing Image > Adjustments > Curves applies the adjustment directly to the image layer and discards image information.
  2. In the Adjustments panel, choose Curve Display Options from the panel menu.
    Note: If you chose Image > Adjustments > Curves, expand the Curve Display Options in the Curves dialog box.
  3. Choose any of the following:

    • To reverse the display of intensity values and percentages, choose Show Amount Of Light (0‑255) or Show Amount Of Pigment/Ink %. Curves displays the intensity values for RGB images in a range from 0 to 255, with black (0) at the lower-left corner. Percentages for CMYK images are displayed in a range from 0 to 100, with highlights (0%) at the lower-left corner. After the intensity values and percentages are reversed, 0 is at the lower-right corner for RGB images; 0% is at the lower-right corner for CMYK images.

    • To display gridlines in 25% increments, select Simple Grid; to display in 10% increments, choose Detailed Grid.

      To change the gridline increment, Alt-click (Windows) or Option-click (Mac OS) the grid.

    • To display color channel curves superimposed on the composite curve, choose Show Channel Overlays.

    • To display a histogram overlay, choose Show Histogram. For more information on how to read a histogram, see About histograms.

    • To display a baseline drawn on the grid at a 45‑degree angle, choose Show Baseline.

    • To display horizontal and vertical lines to help you align points as you drag relative to the histogram or grid, choose Show Intersection Line.