The Levels command corrects tonal ranges and color balance issues. With this command you can fix poor exposure. Additionally, you can perform color correction by manually identifying a white point and black point in the image. Nearly every image can benefit from making a Levels adjustment.
To understand Levels, you must be able to read a histogram. This graph works as a visual guide for adjusting the image. The Levels adjustment has its own histogram that is visible when working in the Adjustments panel. You may also want to call up the Histogram panel (Window > Histogram) and leave it open while color correcting to help you spot issues in color and contrast. You can also expand the Histogram panel by clicking the submenu and choosing All Channels View. Let’s give the command a try.
1. Add a Levels adjustment layer by clicking the Levels icon in the Adjustments panel. Levels is also available from the Adjustments menu (Image > Adjustments), but the adjustment layer is more flexible for future modifications.
2. This photo was shot under mixed light, but you can reset the black and white points of the image to fix the exposure. In the Adjustments panel, move the white Input Levels slider to the left. This affects the image’s white point and allows you to reassign where white should begin in the image.
3. Move the black Input Levels slider slowly to the right. The more you move the black slider to the right, the more contrast is introduced into the image.
4. The true power lies in the middle (gray) Input Levels slider. By moving this slider, you can modify the gamma setting. Effectively, you can use the middle Input Levels slider to change the intensity of the midtones. This adjustment can be made without making dramatic changes to the highlights and shadows, and lets you better expose an image. Move the slider to the left to add light; move the slider to the right to subtract light.
In the future if you need to edit the adjustment, simply select the adjustment layer in the Layers panel and manipulate the controls in the Adjustments panel.
TIP Rinse and Repeat
If you have several images from the same camera or shoot, they may need the same Levels adjustment. The Save button allows you to save a Levels adjustment (to the folder that contains the image is a good place). You can then click the Load button to apply that adjustment to another image.
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