This is how the image looked before an intervention by Curves.

We love the Curves tool because it’s one of the most powerful in Adobe Photoshop, and the most versatile, too. Use it to add contrast just where you want it, brighten or darken an image, and even correct color. But because it involves a graph instead of the more intuitive sliders, it can be confounding for first-time users.

Curves simply graphs—and lets you correct—the tones of your image. As with the histogram, the darkest tones are represented on the left, and the brightest on the right. When viewing an RGB image, the curve line begins at the bottom left and goes along a straight diagonal to the top right. As you add points on that line and move it up or down, your image changes.

The good news: The Curves tool is much harder to explain than it is to use. So, to make it a little easier to understand, here are a few of the most common curves you can implement, and what they do. Try them on your images to make them look better.