Task 3 How to Improve Contrast with Curves

Task 2 showed how to use the Levels dialog box to set the white point and the black point of an image, thus optimizing the tonal range for the image. You can use the Curves dialog box to increase the contrast in the image, allowing you to selectively enhance image details. If the image seems flat or lacking in contrast, curves can make a dramatic improvement. Curves provide complete control over every color and tonal area of your image, as opposed to the Levels command (see the preceding task) or the Shadow/Highlight command (see the next task), which automates edits to specific tonal areas.

1. Open the Info Palette

Open the image you want to affect. Select Window, Info to open the Info palette.

2. Open the Curves Dialog Box

Select Image, Adjustments, Curves to open the Curves dialog box.

3. Set the Black and White Points

Follow the steps in Task 2 to set the black and white points for the image. Use the Eyedropper icons in the Curves dialog box rather than those in the Levels dialog box.

4. Darken Shadows

Click the lower-left portion of the diagonal line in the Curves dialog box to place a point on the line. If necessary, slowly drag the point you placed downward to darken the shadow areas in the image.

5. Brighten Highlights

Click the upper-right portion of the diagonal line in the Curves dialog box to place a point on the light-areas portion of the line. Slowly drag the point up to lighten the highlights, increasing the overall contrast, especially in the midtones. Click OK to apply the effect.

6. View Results

Compare the final result of the Curves adjustment shown here to the image from step 1. Notice the improved detail and clarity in the adjusted image.

How-To Hints

Checking Input and Output Values

In the Curves dialog box, watch the Input and Output values to understand exactly what changes you're making to the curve. The Input value refers to the original pixel value (for example, a midtone value of 128). Clicking at an Input value of 128 and dragging up to an Output value of 160 means that all pixels originally valued at 128 are now a lighter value of 160. In addition, all pixel values around the input value are lightened so that the effect is applied smoothly. Keep the curve shape smooth, and the effect will look natural.