Photoshop CC: The Missing Manual, 2nd Edition

Working with Curves

The last stop on the Color Correction Express is Curves, the most powerful—and fear-inducing—adjustment in all of Photoshop. The basic idea is that, by curving a diagonal line on a grid, you change the brightness of the pixels in your image. Instead of three main adjustment sliders like you get with Levels (shadows, highlights, and midtones), Curves gives you up to 16 adjustments. (The Curves grid shows up in the Properties panel, just like Levels.) But that’s not as scary as it sounds.

If you survived the section on Levels relatively unscathed, you already know a ton about Curves. For example:

• You can use Curves as an adjustment layer so that it’s nondestructive, and you can use the included layer mask to restrict the adjustment to certain areas.

• A Curves adjustment uses a histogram and the same 256 shades of gray you saw in Levels. It also has the same shadows and highlights sliders (though no midtones slider), and it harbors the same trio of eyedroppers for resetting the black, white, and gray points (The Levels Eyedroppers). So far so good!

• You can Option-drag (Alt-drag on a PC) the shadows and highlights sliders to find the darkest and lightest areas of your image, like you learned on The Levels Eyedroppers.

• You can use Curves to correct an image using the Info panel and the Color Sampler tool, and you can type target values into the Properties panel’s Input field. To summon the Input field (shown in Figure 9-20), click a point on the curve (you may need to resize ...