By the Book: This article is an excerpt from The Adobe Photoshop CS3 Book for Digital Photographers, by Scott Kelby (copyright 2008; reprinted by permission of Pearson Education and New Riders).
As far as digital technology has come, there’s still one thing that digital cameras won’t do: give you perfect color every time. In fact, if they gave us perfect color 50 percent of the time, that would be incredible. But unfortunately, every digital camera sneaks some kind of color cast into your images. Here’s how to get your color in line.
In Adobe Photoshop CS3, open the photo you want to color correct. Under the Image menu, select Adjustments: Curves (or press Command-M). Curves is the hands-down choice of professionals for correcting color, because it gives you a greater level of control than other tools, such as Levels, which pretty much limits you to just three adjustment sliders.
First, we need to set some preferences in the Curves dialog box so we’ll get the results we want when color correcting. We’ll start by setting a target color for our shadow areas. To do so, double-click on the Curves dialog box’s black Eyedropper tool. This brings up the Color Picker. In the R, G, and B (Red, Green, and Blue) fields of this dialog box, enter the number 10 . Now click on OK to save these numbers as the target shadow settings. Because these values are evenly balanced (they’re all the same number), our shadow areas won’t have too much of one color, and by using 10, we get dark shadows while still maintaining shadow detail in our prints.
Now we’ll set a preference to make our highlight areas neutral. Double-click on the white Eyedropper. The Color Picker will appear, asking you to select a Target Highlight Color. Enter 243 in the R, G, and B fields. (To move from field to field, just press the tab key.) Click on OK to set those values as your highlight target color.
Now set your midtone preference. You know the drill: Double-click on the midtones Eyedropper (the middle of the three Eyedroppers). Enter 133 in the R, G, and B fields. Then click on OK to set those values as your midtone target color. That’s it—you’ve done all the hard work. The rest is pretty easy.
If you still have the Curves dialog box open, click on OK to exit it for now, and you’ll get a warning dialog box that asks whether you want to save the new tar-get colors as defaults. Click on Yes, and from this point on, you won’t have to enter these values each time you correct a photo—they’re now the default settings.
Now that you’ve entered your target-color preferences in the Curves dialog box, you’re going to use the same Eyedropper tools to do most of your color correction work.
Let’s start by setting the shadows. Press Command-M to bring the Curves dialog box back up. Look at the photo and find something that’s supposed to be black. In most photos, this won’t be a problem—you’ll see a dark area of shadows or a black car tire, for instance. But if you can’t find something that’s supposed to be black, then you can have Photoshop show you exactly where the darkest part of the photo is.
There are two sliders directly under the curve grid that can help you. Press and hold the option key and click on the left slider (Shadow). Your image area will turn solid white. As you drag the slider to the right (while still holding the option key down), the first areas that appear on screen are the darkest parts of your photo. Remember where those areas are (in our example, it’s the shadow under the first pot on the left).
Now that you know where your shadow area is, drag the Shadow slider back to the left, and release the option key. Now click on the black Eyedropper, and (while the Curves dialog box is still open) click once on that shadow area in your photo. The color cast will be removed from the shadow areas.
Now, on to setting the highlight point: Find something that’s supposed to be white. Again, this is usually pretty easy, but if you can’t find something white, you can use the trick you just learned to have Photoshop show you where the lightest part of your photo is. Press and hold the option key, but this time drag the right-hand slider (Highlight) to the left. The screen will turn black, and as you drag the slider to the left, the first white areas that appear are the lightest parts of your image.
Now that you know where your highlight area is, drag the Highlight slider back all the way to the right, and release the option key. Click on the white Eyedropper, and click once on that highlight area. Try and look for a white area that has some detail (rather than clicking on a specular highlight, which is a blown-out highlight area with no detail, like the sun or a bright sun reflection on a chrome car bumper).
Now for your third click: finding something that’s supposed to be a neutral gray. This one’s a little trickier, because not every photo has a neutral gray area, and the Curves dialog box doesn’t have a “find the gray” trick, as it does for shadows and highlights (for a workaround, see “Finding a Neutral Gray”). In the example photo, the neutral gray is in the edge of the large vase on the ground. This click neutralizes the color cast in the midtones.
Updated at 4:25 p.m. PT on April 30 to correct a production error that incorrectly displayed the Command-M keyboard command.