How to Use Curves to Find Highlights and Shadows in Adobe Photoshop CS6
Without Adobe Photoshop CS6, you’d spend a fair amount of time trying to locate the lightest and darkest parts of an image. Fortunately, you can cheat in Photoshop by using some features in the Curves panel. Here’s how to access the panel:
With an image worthy of adjustment — one that isn’t perfect already — choose Window→Layer (if the Layers panel isn’t already open).
Click and hold the Create New Fill or Adjustment Layer button at the bottom of the Layers panel and select Curves.
The Adjustments panel appears with the Curves panel active.
Notice the grayed-out histogram behind the image in the Curves panel. The histogram helps you determine where you need to adjust the image’s curve.
If working with RGB confuses you, simply select Curves Display Options from the panel menu in the upper-right corner of the Adjustments panel. When the Curves Display Options dialog box appears, select the Pigment/Ink % radio button and click OK.
Note that in the Curves panel, you see a Preset drop-down list that offers quick fixes using standard curves for certain corrections. These settings are great for quick fixes, but for the best image, create a custom curve.
The first thing you need to do in the Curves panel is determine the lightest and darkest parts of the image — referred to as locating the highlight and shadow:
Before starting the correction, click the Set Black Point eyedropper once.
Hold down the Alt (Windows) or Option (Mac) key and click the Shadow input slider.
If you did not change your Curve Display Options to display Pigment/Ink %, your highlight and shadow sliders will be opposite of what appears here.
When you Alt-click (Windows) or Option-click (Mac), the clipping preview turns on, revealing the darkest area of the image.
If you don’t immediately see a dark area in the clipping preview, you can drag the shadow input slider to the left while holding down the Alt key or Option key. Note where the darkest area of the image appears.
Hold down the Shift key and click directly on the image in that dark region.
This step drops a color sampler on the image that helps you reference that point later.
Repeat Steps 1 through 3 with the Highlight input slider. Select the Set White Point eyedropper in the Curves panel.
Hold down the Alt key or Option key and click the highlight input slider.
Again, you can drag the slider toward the right if the lightest point doesn’t immediately show up.
When you locate the lightest point, as indicated by the lightest point in the clipping preview, you can Shift-click to drop a second color sampler.