The spectacular space battles seen in Star Wars, released in 1977, were created using miniatures, blue screens and optical compositing on plain old celluloid. The film’s computer graphics crew? Four. Behind Star Wars: Episode I-The Phantom Menace, by contrast, was an army of hundreds of digital effects artists. For Episode II, director George Lucas has said, the live-action scenes will be shot using digital movie cameras, leaving not a single scrap of film on the cutting-room floor.

Bits and bytes, in other words, are rapidly replacing crystals of silver on paper or film as the dominant storage medium for two-dimensional images. Because bits are so malleable, video artists can give visual form to an astonishing new range of ideas.

For most people, unfortunately, the process of creating and manipulating digital images remains as arcane as the alchemy of the photographic darkroom. In her new college textbook Computers in the Visual Arts, Anne Morgan Spalter, an artist in residence with Brown University’s Computer Graphics Group, has set out to demystify the subject. The result is not so much a textbook as a friendly, comprehensive, mostly non-technical introduction to the tools and techniques used by digital artists. Anyone who has marveled at Toy Story or A Bug’s Life will find it a stimulating tour.

Spalter reveals, for example, that “a pixel is not a little square.” It is actually a list of numbers, some for the coordinates of a point on the computer screen and others for the brightness of red, green and blue phosphors at that point. Local or global changes to a digital image can be made simply by performing addition, subtraction or other mathematical operations on these numbers. This, in fact, is all that high-priced photo-editing programs like Adobe Photoshop really do, Spalter notes.

While she explains the workings of photoediting software in some detail, Spalter never loses sight of the history, theory and implications of the rise of the bit in visual discourse. “Our concept of visual truth may come full circle as new technologies come into play,” she writes. In the 16th century, Europeans saw new linearperspective paintings as miraculously realistic; 19th-century photography increased this realism by storing actual light patterns. “But in a postphotographic world, the strength of that connection [to reality] is again uncertain,” Spalter concludes sagely. “Every photograph becomes a painting.”