Digital Data Pioneer

May/June 2011

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Digital Data Pioneer

Photo: Courtesy Joan Mitchell

When you email a family photo, you might thank Joan Mitchell. Her work on data compression helped revolutionize the way we send, store and print digital images. She has 110 patents to her credit and has received many awards, including being an IBM fellow and 2011's IEEE Masaru Ibuka Consumer Electronics Award.

After receiving her PhD in physics from the University of Illinois at Urbana-Champaign, Mitchell was hired at IBM's T.J. Watson Research Center. It was 1974, and the PC had not yet been invented; Mitchell had used only punch cards and teletype machines. But computer science hooked her from the first. "I absolutely loved it," she says. "It completely fit me."

On a whim, Mitchell sat in on a lecture about data compression at the Research Center. She left the room with a whole new career path.

Digital transfer of information faced two hurdles: Data was often too big to be easily sent or stored, and no international agreement existed on a standard way to compress it. In 1979, Mitchell helped develop and negotiate an international fax standard. Then she moved on to images. In the late 1980s, she became a key member of the international Joint Photographic Experts Group, where she helped create and edit a standard algorithm that could reduce a picture's size without significantly degrading its quality—the familiar .jpeg suffix on digital images. Mitchell also contributed to the Moving Pictures Experts Group (a.k.a. MPEG) for video.

She and IBM's William Pennebaker co-wrote books on both standards. Their 1992 book on JPEG, affectionately known as "The Pink Book" because of its cover, is still the definitive textbook.

Mitchell modestly describes her career as a series of lucky coincidences. But Pennebaker insists that Mitchell's intelligence, persistence and hard work made the most of every opportunity that came her way. Sometimes only church (Mitchell is a Christian Scientist) and scuba diving classes kept her from working through the weekends. "I'd be so busy inventing I'd be up 10 or 12 times a night," she admits.

Though Mitchell was often the only woman in the room during her studies and career, she decided early on that being female wasn't going to stand in her way. "My grandmother got two degrees in physics from Stanford in 1911," she points out. "If she could do it, I could do it." In addition to her technical publications, she wrote an advice book, Dr. Joan's Mentoring Book: Straight Talk About Taking Charge of Your Career. Mitchell says mentoring relationships were a highlight of her life—not just of her career. "I always learned as much as I taught."

Now retired, Mitchell became legally blind last year, but she hopes the condition is temporary. "I'm very blessed with family and friends," she says, "and I intend to have a marvelous retirement."

Susan Fry, '91, MA '92, is a writer in Los Gatos, Calif.

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