THE PROCESS OF MAKING COLOR IMAGES

DAVID H. FREEMAN

Advances in computer technology are providing new and exciting possibilities for image-making. Millions of people, including children, are using image-processing software to experiment with their photographs. Most do so without knowing anything about the physics, mathematics, and chemistry of color, but rely instead on computer software to make the process relatively simple.

The technology that makes color imaging possible goes back to Sir Isaac Newton, who explained why white light could make rainbows, and to James Clerk Maxwell, who explained how rainbows could be constructed from the three primary colors. Their insights combine to make the principle of color separation, which underlies color photography, printing, and videos. Color separation makes it possible for computer images to be input through a scanner or a digital camera and be output to a video monitor using only red, green, and blue light. When the image is printed, only four dyes are used, i.e., cyan, magenta, yellow, and black.

There are a number of good software programs for color image processing, and even a beginner can learn to work in a modern “digital darkroom” to produce excellent color prints. No chemicals are required beyond the ink cartridges for your printer. For the most part, professional artists, designers, and photographers are using Adobe Photoshop software, which is not inexpensive. However, you can become a digital buff with similar, but less costly, software called Adobe Photoshop Elements.

Let’s take a mental tour of how to use a computer to change and, we hope, enhance color images. To start, imagine your computer screen showing an image of a sandy beach at twilight. If you decide the image is perfect, send it off to the printer. If you want to make some changes, though, this is when the fun begins. Do you want to adjust all of the image, or just a part, like the yellow hat lying on the sand? To work on just that part of the image, you will need some specific tools. You can select the hat by its color because it is yellow, or select it by tracing its outline. While you work on such a selection, the rest of the image remains unchanged. Now, it’s time to think like an artist. Maybe the hat should be more yellow-green, or a shade of orange. Or maybe the rim outline should be brighter. You can use a graphics tablet that features a tool much like a paintbrush or pencil and experiment away. Or, you can throw paint with a digital “bucket,” and regulate the opacity of the paint you are applying. After each such change, you decide whether to keep the change or to “undo” it.

Digital images may contain over 17 million colors, but don’t be overcome by so many choices. Color pickers are available to help narrow down the specific colors to apply. Colors can also be “shifted” by applying a color filter comparable to what might be placed over a camera lens. There are many ways to experiment: blend or shift colors; enhance an image by making it lighter or darker; or adjust its contrast. Such changes can be done (or undone) quickly with just a few taps on your keyboard.

Photoshop software offers plenty of processing and editing options. Problems with perspective or with other elements of photographic composition can often be corrected. For the scientifically minded, there are ways to measure spatial coordinates, angles, and color number values in a picture. If you are artistically inclined, you can overlay and blend multiple images using transparent layers. There is practically no limit to the number of ways to reshape, sharpen, blur or, more generally, make a photograph better. You can even change it into a sketch or a painting.

In today’s fast-paced world, a digital camera or scanner can deliver an image to your computer in a matter of seconds. Learning how to process images has gotten easier thanks to the many books and courses that are available to the public. With just a little help of this kind, you, too, can join the ranks of amateur and professional photographers who have learned to use computers to take their photographic experiments to new levels.

David H. Freeman (CC ’77), a professor at the University of Maryland from 1973-98, published 75 articles on analytical chemistry, and developed chemical micro-standards while at the National Bureau of Standards (now NIST) from 1965-73. He now teaches digital photography at the Washington School of Photography

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