The Curves interface is more complex than Levels, which scares away many users. Levels gives you three control points (highlights, midtones, and shadows), but the Curves adjustment allows for up to 16 control points, which opens significantly more options when adjusting color and exposure.
Let's try the Curves command on a practice image.
- Close any open files, and then open the file Ch10_Curves_Practice.tif from the Chapter 10 folder (see Figure 21).
- Add a Curves adjustment layer by clicking the Curves button in the Adjustments panel. When you first open the Curves interface, there are two points (one for white and one for black).
- Add a single control point in the middle of the line (click at an Input Value of 50%), as shown in Figure 22.
- Pull this new control point down (toward the lighter area on the y axis) to lighten the image (see Figure 23), or pull the point up to darken the image. Notice that the Input and Output values update as you drag (see Figure 24).
- The adjustment is applied gradually throughout the entire image. Multiple points can be employed for contrast adjustments based on tonal range.
The primary advantage of Curves is that you have precise control over which points get mapped (whereas you don't in Levels). Another benefit is that Curves adjustments use a curved line to make adjustments—as opposed to Levels, which uses only three control points. In this way, color correction can be applied in a more gradual manner, without the hard clipping that can be associated with Levels.
Let's check out the Curves command now.
- Close any open files, and then open the image Ch10_Curves.tif from the Chapter 10 folder (see Figure 25).
- Add a Curves adjustment layer by clicking the Curves icon in the Adjustments panel. The curve has only two points on it—one representing the black point and one representing the white point.
- It's time to add more control points to refine the curve. To do this, you'll use a Curves preset. Click the drop-down menu to select a Curves preset in the Adjustments panel. Choose the Strong Contrast (RGB) preset (see Figure 26). Notice that the image now has more contrast in the shadows and highlights, and more visual "pop."
- Experiment by adjusting the five control points. Try to further emphasize the shadows in the image (see Figure 27). Continue to experiment by moving the control points (see Figure 28). You can use the up- and down-arrow keys for precise control.