Colorize your world
Excerpted from “Adobe Photoshop CS One-on-One” by Deke McClelland.
One of the major uses for the Hue/Saturation command in Adobe® Photoshop® is colorization. You can override the colors in a color photograph—particularly one in which the colors aren’t in great shape. Or, more popularly, you can use the command to add color to a grayscale image. Hue/Saturation makes both tasks a breeze. But its limit of one Hue value and one Saturation value per operation makes it a flimsy tool for the job.
My preferred method for colorizing involves a little-known function called Gradient Map, which allows you to substitute luminosity values with as many hue and saturation values as you like. Problem is, this command is so far outside the mainstream of most Photoshop users’ experience, and Hue/Saturation is so commonly employed for colorizing, that I feel compelled to do something I don’t normally do in an exercise—compare and contrast. Therefore, in the following steps, we’ll make use of both the Hue/Saturation and Gradient Map commands, and you can decide for yourself which is better (even though, truth be told, I’m pretty confident about your verdict).
1. Open an image.
Open a grayscale image. The grayscale image I chose hails from a black-and-white slide I shot back in high school. (Don’t ask how long ago that was; thanks to a non-disclosure agreement with my vanity, I’m not at liberty to say.) I like the worn quality of the slide, so I enhanced it a bit with the Shadow/Highlight command rather than retouching it away. However, it’ll look livelier after we add color.
2. Convert the image to RGB color.
A grayscale image contains just one channel of information and therefore is incapable of displaying colors. Before you can add color, you have to add the channels. To do so, choose Image > Mode > RGB Color. If you have the Channels palette open, you’ll see the one Gray channel turn into Red, Green, and Blue, plus the RGB composite. Otherwise, the photo won’t look any different because the new channels are identical to the original one, as is necessary to maintain a neutral color balance. But you can take my word for it, the image is now ready for color to blossom.
3. Choose the Hue/Saturation command.
Choose Image > Adjustments > Hue/Saturation to display the Hue/Saturation dialog box.
4. Turn on the Colorize check box.
Located in the lower-right corner of the dialog box, the Colorize check box applies the Hue and Saturation as absolute values. By this, I mean that all pixels are assigned one uniform Hue value and one uniform Saturation value. The moment you turn on Colorize, Photoshop changes the Hue to 0 degrees and the Saturation is 25 percent, which turns the entire image to a low-saturation red, as shown below.
5. Adjust the Hue and Saturation values.
At this point, I encourage you to experiment. A Saturation of 0 percent invariably results in gray; 100 percent delivers the most vivid color Photoshop can achieve.
Tip: While you experiment, you may want to try out a wonderful little trick called “scrubbing,” which is new to Photoshop CS. Move your cursor over the word Hue or Saturation and drag to scrub the value up or down. Press Shift as you drag to change the value in increments of 10. If you like this technique, take heart—it works in most dialog boxes and palettes. If not, take heart—you don’t have to use it.
For my part—and you’re welcome to follow along with me if you like—I entered a Hue of 40 degrees and a Saturation of 30 percent. The result is an orange-amber duotone, so called because it contains two tones, black and the 40-degree amber.
6. Cancel the adjustment.
Okay, that was all very interesting, but not good enough. Why? Because the moment you turned on the Colorize check box, you lost all selective control. The Edit pop-up menu dimmed, and thus you lost the ability to adjust the hue and saturation of individual colors. Your best bet is to press the Esc key or click Cancel to abandon your changes from Steps 3 through 5, and then turn to the little-known Gradient Map command for a better solution.
7. Choose the Gradient Map command.
Located with the other color commands in the Image > Adjustments submenu, Gradient Map substitutes the luminosity values in the image with the colors in a gradient. Strange as this may sound, it’s just the ticket for quality colorization. Armed with Gradient Map, you can swap every single gray value, from black to white, for a specific color. And all you need to make this happen is a gradient.
Incidentally, for those who may be wondering, a gradient is a continuous fountain of colors. The gradient may transition from black to white, from one color to another, or between a whole slew of colors, as illustrated by the examples below.
Tip: For what it’s worth, Photoshop offers yet another colorization function, Image > Mode > Duotone, that lets you print a grayscale image using a combination of two to four colors. Although ostensibly a professional-level tool, I know of few professionals who regularly use it thanks to its arcane implementation. It’s a powerful command, and I encourage you to try it—never thwart the enthusiasm of an eager student, I always say—but Gradient Map provides better feedback, more color choices, and the undeniable advantage of a more straightforward approach.
8. Create a custom gradient.
Photoshop’s predefined gradients don’t work very well for colorization. So I’ve created a trio of colorization gradients for you to play with. For this tutorial, we’ll simulate a gradient I created called Quadratone Supreme.
9. Open the Gradient Editor.
A gradient map behaves a lot like the Curves command because it lets you lighten or darken individual luminosity values. To edit colors in a copy of the default gradient, click inside the gradient bar to display the Gradient Editor dialog box.
Although the dialog box is brimming with options, most of the action centers on the gradient bar. The boxes above the bar control the opacity of the gradient, and have no effect on the outcome of the Gradient Map command. The boxes below the bar let you add key colors to the gradient. Because they determine the position of the colors, they are known as color stops.
Add stops to the gradient to match the Quadratone Supreme gradient settings shown below. To change the colors used in the gradient, double-click a stop and select a new color using the Color Picker.
A. Opacity stop(no effect on gradient maps) B. Gradient bar C. Color stops
About the author
In 1985, Deke McClelland oversaw the implementation of the first personal computer-based production department in Boulder, Colorado. In 1986, he became the artistic director for Publishing Resources, one of the earliest all-PostScript service bureaus in the United States. Deke McClelland is a well-known expert and lecturer on Adobe Photoshop, Illustrator, InDesign, and the broader realm of computer graphics and design. To date, he has written 85 books that have been translated into 24 languages, with more than 4 million copies in print.
