The Curves feature is similar to the Levels feature but it provides more precise control over the tonal range. Whereas Levels uses highlights, shadows, and midtones to correct the tonal range, Curves lets you adjust any color along the tonal range, instead of only three variables, without affecting other colors. For example, you can use Curves to correct for a color cast caused by lighting conditions.

The grid in the Curves dialog box illustrates two brightness values:

The horizontal axis represents the original brightness of the pixels, shown in the Input box.

The vertical axis represents the new brightness values, shown in the Output box.

When you first open the Curves dialog box, the diagonal line indicates that no changes have been made, so the input and output values are the same for all pixels.

To adjust a specific point in the tonal range:

  1. Select the image.
  2. Do one of the following to open the Curves dialog box:
    • In the Property inspector, click the Plus (+) button beside the Filters label, and then select Adjust Color > Curves from the Filters pop-up menu.

    NOTE

    If the Property inspector is partially minimized, click the Add Filters button instead of the Plus button.

    • Select Filters > Adjust Color > Curves.

    NOTE

    Applying a filter from the Filters menu is destructive; that is, it cannot be undone except when Edit > Undo is an option. To maintain the ability to adjust, turn off, or remove this filter, apply it as a Live Filter, as described in the first bulleted option in this step. For more information, see Using Live Filters.

    This is a picture of the feature being described.

    Curves dialog box

  3. In the Channel pop-up menu, select whether you want to apply changes to individual color channels or to all colors.
  4. Click a point on the grid's diagonal line and drag it to a new position to adjust the curve.
    • Each point on the curve has its own Input and Output values. When you drag a point, the Input and Output values update automatically.
    • The curve displays brightness values of 0 to 255, with 0 representing the shadows.

      This is a picture of the feature being described.

      Curve after dragging a point to adjust

    TIP

    You can also adjust highlights, midtones, and shadows automatically by clicking the Auto button in the Curves dialog box.

To delete a point along the curve: