With the Levels adjustment, you can control the contrast and the tonal range of the photo. You can adjust the black point, shadows, midtones, highlights, and white point settings to brighten up an image, add more contrast to an image. You can also use Levels to adjust the RGB change the look of specific colors (red, green, and blue).
A handy color histogram shows just how much of the image colors are in the shadow, midtone and highlight areas of an image, and gives you a clearer idea of what needs to be adjusted.
There are five sliders you can work with: black point on the left, gray point in the middle, white point on the right, and two quarter-tone sliders. Each one of the sliders is responsible for the different parts of an image tonal range – black and white point sliders let you adjust the darkest and brightest areas of a photo, while the midtone slider deals with all the colors that come in between.
Essentially, dragging the black point slider to the right makes the image darker, dragging the white point slider to the left makes the image brighter, while dragging the midtones and quarter-tone sliders shifts all the image colors to the darker or the brighter side depending on the direction you’re dragging.
Tap and turn on Levels.
Drag the sliders to adjust the colors, brightness, and contrast of a photo:
Black point: Dragging the black point slider sets a new black point in an image. In other words, lets you redefine the darkest areas (shadows) of an image to bring them closer to pure black and increase contrast.
Grey point: Dragging the grey point sets a new grey point in an image. You can drag the slider to the right to make all image midtones brighter and to the left to darken them without affecting the dark blacks and bright whites.
White point: Dragging the white point slider sets a new white point in an image. This way, you can redefine the brightest areas (highlights) of an image to bring them closer to pure white and increase contrast.
Quarter-tone: Drag these sliders to adjust the tones in between either the shadows and midtones, or midtones and highlights, without affecting the other tones too much.
Important: If the dark or bright tonal values of an image were close to pure blacks or pure whites to begin with, re-adjusting them might result in blown-out shadows or highlights and image may lose detail.