Access the Curves Panel in Photoshop CS5
You can fix an image created in less-than-perfect lighting using Photoshop Creative Suite 5 features that are found 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.Access the Curves panel with the Create New Fill or Adjustment Layer button.
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 you’re correcting in RGB (as you should be), the tone curve may be the opposite of what you expect. Instead of light to dark displaying as you expect, RGB displays dark to light.
Think about it: RGB is generated with light, and no RGB means that there’s no light and you therefore have black. Turn on all RGB full force and you create white. Try pointing three filtered lights — one red, one green, and one blue. The three lights pointed in one direction create white.
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 dialog box appears, select the Pigment/Ink % radio button and click OK.
If you need a little more space in the Curves panel, click the Expanded View button at the bottom of the Curves panel. The panel enlarges.
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.