Correcting Tone and Exposure - Beginning Photo Retouching and Restoration Using GIMP - page 49

Figure 3-14. The Levels dialog
The Levels dialog displays a histogram, which is a graphical representation of the pixel values across
the image, ranging from 0 (pure black) to 255 (pure white). Factors such as image tonality and exposure
determine the shape of the histogram.
Levels allows you make changes on a composite of the red, green, and blue channels (Value) by default.
Changes can be made on each color channel individually, which we'll look at in Chapter 4.
Tutorial 2: Correcting Contrast with Levels
In this exercise, we're going to improve the contrast in this image. As you can see in Figure 3-15 , it has
a rather flat tone. The highlight areas are dingy; the shadow areas are gray and muddy. A simple levels
adjustment will make this photo pop out a lot more.