Kim Kardashian has practically made a living off her curvaceous figure. But the E! network celeb was looking a little less shapely in Complex magazine in April, her body reduced about a dress size, her legs smoothed to near-perfection.

How did readers know? Complex accidentally posted a pre-Photoshopped image of Kardashian on its website -- before her thighs, arms and waist had been digitally sculpted. In a matter of hours the photo was gone. But in that brief time span, those who spotted it got a little reminder that we should think twice about taking photographs at face value.

"My belief," says Scott Kelby, president of the Florida-based National Assn. of Photoshop Professionals, "is that every single major magazine cover is retouched. I don't know how they couldn't be." But don't stop there. Aside from U.S. newspapers, most of which do not permit photos to be manipulated, it's quite possible that the vast majority of images seen in the public arena have been altered.

Photoshop, the go-to graphics editing program that got a foothold in the 1990s, has become so ubiquitous that most of us gaze at faces, bodies and landscapes, not even registering that wrinkles have been diminished, legs lengthened and the sky honed to a dream-like shade of blue. And, unlike its predecessor, airbrushing, anyone can use it.

But Photoshop's popularity has proven to be divisive. While some laud it for its ability to allow people -- and things -- to look their best in a photograph, others see it as a vehicle for feeding our culture's desire for uber-perfection.

"I think the perfect bodies we're seeing in magazines that are Photoshopped have a terrible effect on how women feel about their own bodies," says Montana Miller, assistant professor in the department of popular culture at Bowling Green State University in Ohio.

One theory about retouching in advertisements is that it's done to create an aspirational concept of beauty that inspires women to buy more products. Miller's heard another: that the goal of showing perfect images is to make women feel bad about themselves -- also making them buy more beauty products.

Kelby, who also writes a blog on Photoshop, doesn't believe it's a malevolent force; in fact, he sees it as practical and cites the example of singer Faith Hill.

In 2007, the fashion website Jezebel posted unaltered images of Hill that were shot for a Redbook magazine cover. In comparing them to the finished product, it appeared that Hill got a makeover, including erased crow's-feet, excised back fat and a slimmer arm.

The fallout was huge -- the Jezebel post generated more than 1.3 million views, and was picked up by ABCNews.com, VH1.com, TMZ.com and a number of blogs. Many commenters were angry that an already attractive woman had her image altered to appear on the cover of a national magazine. (Redbook declined to comment for this story.)

"If you met Faith Hill in person," Kelby says, "you would think she's absolutely beautiful. And when you take her picture, you will see every flaw that you never saw in person. Those flaws not only become visible, but magnified. . . .

"If I were talking to someone, I'd look at their eyes, not at the blemish on the side of their face. But as soon as you open up that photo on a 30-inch monitor, you'd say, 'Oh my gosh, where did that come from?' "

What the brain perceives in a still photo is vastly different from what it perceives in real life, according to Dr. Dale Purves, director of the Center for Cognitive Neuroscience at Duke University in Durham, N.C. Up close and personal, "every second you're getting a series of images of a person that you're kind of blending together, and that would be a little more forgiving." What we're taking in, he adds, is a load of stuff, including clothing, personality and smells -- elements that can evaporate in two dimensions.

When it comes to editorial photos for magazines, it's common for several different people -- photographers, professional retouchers, photo editors, art directors, publishers -- to have a say about an image. Although some editors insist celebrities don't have final say on how images will be altered, "If they're big enough, they do get [final approval]" says Howard Bragman, chairman of the Fifteen Minutes publicity and media company and author of "Where's My Fifteen Minutes?"

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Retoucher Amy Dresser sits at a computer monitor in her home office scanning a portrait of an auburn-haired model to demonstrate how she uses Photoshop. She deftly zaps a few small moles and then peers at a small white patch just below the model's eye before obliterating that too.

"I think one of my main objectives," she says, "is to erase distractions. When you look at an image, sometimes people can't focus on what they're supposed to focus on because there's something going on in the background."

She adds, "I don't have a rule that a mole near her armpit equals bad. It's really case by case. I don't think anything is universally bad."

Dresser is considered one of the top freelance retouchers in Los Angeles. Her portfolio includes work on celebrity, advertising and model photos (Britney Spears, Gwen Stefani, Kat Von D, Lil Wayne, Dita Von Teese) for editorial work, and promotion, as well as big-budget ad campaigns.