When Lenna Sjööblom posed for PLAYBOY—wearing little more than a feathered floppy hat, a pink boa and an arresting gaze—the Swedish model had no idea she would become part of computer history. Shot by Dwight Hooker, Lenna’s Centerfold (cropped above) played a key role in the development of electronic image processing after engineers at the University of Southern California chose it as a test photo in 1973. Grabbing a colleague’s magazine, the researchers scanned the modest upper third of the fold-out and included it in a conference paper. By the time the digital revolution dawned years later, it had been used countless times as a basis for judging compression effects, the photo’s precision-perfect detail, shading and texture making it a useful tool. In the world of computer imaging, Lenna became known as “the first lady of the internet.”

It would never have happened if Lenna hadn’t visited her cousin in Chicago and then decided to stick around after quickly landing gigs as a model. America’s independent streak also attracted her. “The modeling work may have influenced my decision to stay,” she said, “but I think it was more the freedom here.” Not only did Lenna help lay the foundation for JPEG and MPEG standards (and become the fantasy pinup for plenty of computer programmers), the issue she appeared in also became the most popular PLAYBOY of all time. Forget breaking the internet—Lenna helped make it.