Every digital image contains a range of tonal values, distributed over a range of light and dark tonal values. Often, even with properly exposed images, you'll want to redistribute these tonal values to meet aesthetic or quantifiable criteria. There are several ways to do this with Lightroom.
Lightroom's processing tools are organized systematically, providing a rough order to follow as you work on your image. After you have determined the proper Lightroom white balance (as we discussed in the previous section), it's time to start working on the tonal values found under the Basic tone pane or directly in the Histogram itself. Figure 5-28
A good place to start is with Auto. Figure 5-29 When you click on the Auto button (circled), Lightroom creates a made-to-order tone map based on the individual characteristics of a particular image. It does not affect the Clarity, Saturation, or Vibrance controls. Auto often produces satisfactory results, but not always.
For example, in this image, Auto successfully darkened the light blue wall around the subject, but it darkened the subject too much at the same time. Figure 5-30 a I often keep the Auto setting, even if it's not perfect, and fine-tune the results ...