While you can certainly make a bad photo look good by dragging the Adjust panel’s sliders to and fro, learning to use them effectively involves learning about its histogram: the colorful little graph at the top of the panel.

The histogram is the heart of the Adjust panel (it lives at the top of the panel—see Figure 5-12). It’s a self-updating visual representation of the dark and light tones that make up your photograph. If you’ve never encountered a histogram before, this may sound complicated. But the Adjust panel’s histogram is a terrific tool, and it’ll make more sense the more you work with it.

Within each of the histogram’s superimposed graphs (red, blue, green), the scheme is the same: The amount of the photo’s darker shades appears toward the left side of the graph; the lighter tones are graphed on the right side.