Celebrities are considered attractive at least in part because they’re suited to the technology of the age. The transition from silent movies to talkies destroyed many actors’ careers, as did the shift from black-and-white to color. While almost all prime-time TV on the major broadcast networks is shot in high-def, there are only 18 million of the pricey, wide-screen sets in use. But that number is expected to more than triple by next year, and the new scrutiny that comes with high-def is already making some on-camera talent nervous. “There are a lot of people who are going to be affected by this,” says Deborah Paulmann, a makeup artist for “Late Night with Conan O’Brien.”

To understand why high-def is so unforgiving, consider the numbers. Today’s new top-of-the-line HD televisions can display two million pixels, nearly 10 times the resolution of a regular, old-style TV set. Also, the screens are the size of a tabletop. Watching a show in high definition is thus rather like being Gulliver in the land of Brobdingnag — where every pore on the giants’ faces looms like a shell-blasted crater. Many new HDTV owners have tuned in to high-definition celebrity events, only to discover that their favorite stars suddenly look downright haggard.

“I’m seeing people in a whole new way,” says Phillip Swann, president of OnHD.TV, an online magazine. “If somebody’s aging or if they’ve got any old acne damage, it just jumps out at you. They’ve got no chance.” The editors of OnHD.TV examined several dozen stars and compiled a list of heartthrobs who (they claim) wither under the unblinking gaze of high-def, including Cameron Diaz (“littered with unfortunate pockmarks”), Jewel (whose makeup “looks like it was done by Ringling Brothers”) and Bill Maher (“scary”). I’ve seen the effect myself: when I recently watched a high-def close-up of Bradley Whitford — a handsome star of “The West Wing” — a normally insignificant mark on his forehead suddenly stood out like a third eye. I couldn’t stop staring.

The high-def format’s merciless gaze isn’t solely a matter of screen resolution. Color is a factor, too. For years, government standards have limited the range of colors available to broadcasters, based on the technological limits of the time. With high-def, more colors can be used, including some formerly forbidden shades of red — which means that blotches, zits and tiny nose-veins can be presented with the brutal clarity of a surgery textbook.

“It’s almost too realistic, too digital and computery,” complains Alexis Vogel, a veteran celebrity makeup artist who recently worked on “Stacked,” a high-def show starring Pamela Anderson. “We’d all like to go back to the old days.” Makeup artists are now engaged in an arms race with the new medium. But they face a paradox: while makeup is more necessary than ever, its artifice is more obvious. You can’t slather on powder when every grain looks like a boulder on your client’s face. And interestingly, many cosmeticians predict that high-def could actually reduce the amount of plastic surgery in Hollywood, because the tiny seams look Frankensteinian at such high resolution. High-def is, in essence, a medium peculiarly unsuited to dissembling. “It’s harder to change people from their natural form,” Vogel adds.

This will probably put an ever-higher premium on genuinely natural beauty — those lucky few people who require virtually no touch-up. Indeed, high-def fans say that some stars look better in the new medium: Anna Kournikova, George Clooney and Catherine Zeta-Jones glow like supernovas, and, Vogel says, “in high-def, Halle Berry’s skin is so beautiful and flawless, she’s almost a genetic freak.”

Clive Thompson is a contributing writer for the magazine.