For the video version see Photoshop Color Correction with the Curves Eyedropper (Video)

Photoshop allows you to quickly correct problems in color and exposure simultaneously using the Curves Eyedropper tool. With a few clicks you can re-map the entire range of light and color values in your photo to be more accurate and eye-catching.

Step 1. Open your photo. The example image shown below has a blue-ish color cast, and it lacks contrast, especially in the blacks, which gives it a washed-out look.

Step 2. Create a Curves Adjustment Layer. The quick way is to click the Adjustment Layer button at the bottom of the Layers Palette and choose Curves from the menu.

Step 3. You'll see three eyedroppers below the histogram in the Curves Dialog. You're going to use these to specify the Black Point, the Gray Point, and the White Point in your image.

Step 4. Select the Black Dropper on the left, and then click in the blackest spot on your photo. Photoshop instantly remaps the light values in your entire photo to make this point true black, and it adjust all the other values accordingly. Your photo should instantly look better.

Step 5. Next, select the White Dropper and click it in the whitest part of your photo. Again, Photoshop instantly remaps the entire tonal range of your image to make this point true white.

Step 6. You may decide that your image looks fine now. But if it has a color cast, you'll need to do the next step and adjust the Gray Point.

Your goal with the Gray Dropper is to find a point that is Neutral Gray in color—it doesn't really matter how light or dark the point is, just that its color, in reality, is equal parts Red, Green, and Blue. If your photo has a color cast, of course, these RGB values may not be equal in the photo. This is why it's often difficult to locate a gray point, unless you have a gray card or some known gray object in your photo that you can click on.

In the example photo, I know the wall in the background is actually gray (concrete is usually a good choice) so I click there to set my Gray point.

If you have a white object in your photo, you can look for a shadow on it to find your gray point. But sometimes it's really difficult to find a gray point in your photo. What to do then?

Some advanced users will create a new layer which averages all the color values in the photo, or use mathematical tricks to find Neutral gray points, but these are time consuming techniques, and even worse, if your photo has a strong color cast it will often simply introduce a different color cast.

Sometimes the best and quickest solution is to just try likely gray points by trial and error until you get one that makes the photo look good to your eye.

PORTRAIT SECRET: In a portrait, you can often fall back on a little trick for the gray point when you don't have any gray objects or clothing in the photo. Try clicking on the whites of your portrait subject's eye. (If you get a red vein, it will throw it way off, so try again.) Not everyone's eyes are equally white, so it works better on some than others. But this has saved me many times!

I often find that after the color has been corrected, the photo is a bit too dark overall. In that case, you can pull upward just a bit on the RGB line (the main line) in the Curves histogram to brighten the entire image.

This description took far longer than the process takes in reality. Once you become familiar with this technique, you can often make this adjustment in just a few seconds. Instantly your photo has more accurate color and more eye-catching contrast!

You can also watch a video version of this tutorial.