Curves enable users to further adjust the overall tonal distribution of an image within the shadow and highlight limits that are set by the Levels tool. Like Levels, the Curve tool has several channel modes to choose from depending on your intent. The combined RGB mode is used to adjust contrast and lighten or darken an image.
- Go to the Exposure Inspector.
- In the Curve dialog, select the RGB tab.
- Click directly on the slope to add a control point in the tonal region that you want to adjust. The upper-right part of the slope adjusts highlights and the center adjusts mid-tones. The bottom or lower-left part adjusts the shadows.
- To lighten or darken the selected region, select and drag (or scroll) a control point up or down respectively to form a curve.
- To decrease or increase contrast in the chosen region, click and drag the control point to the left or right respectively.
- Add more points to the curve to adjust other areas. To remove a control point, click and press delete/backspace or drag it off the curve.
- As an option, you can also add points by selecting the Curve Point Picker and clicking on the area of your image that you want to adjust in the Viewer.