In a FaceTime world, advice to "watch your back" is a warning. Stay alert, be on guard.

We're vulnerable from behind, subject to gossip, innuendo, assault and assassination — of character or otherwise. Perhaps that's why photographs of people's backs are so rare. And so fascinating. There's something covert and voyeuristic about a picture of someone seen from behind.

All sorts of psychological games come into play in "Who's Who: Seeing Back to Front," an intriguing show of about 60 photos at the Minneapolis Institute of Art through Oct. 30. About half the images feature famous people photographed from behind. The other half are frontal images of well-known individuals.

The "back" photos are especially fun because they're a tease. Presuming the subject is famous enough to pop up in a museum show, we scan for clues. A man in black with a guitar on his back? Yep, Johnny Cash. A broad-shouldered guy in cowboy boots and crumpled hat, his right hand itching for the butt of a pistol in an invisible holster? John Wayne on a film set. A slender brunette with child in arms gazing through the ruffled curtains of a Frenchified nursery? Jackie Kennedy and Caroline.

Some of the back photos are immediately recognizable thanks to such clues of haircut, clothing, stance or context. Four mop-topped young men in stovepipe pants and sport coats, gazing at a Victorian brick row house on a cobbled street? The Beatles, 1965.

History stamps others. A man in baggy baseball stripes, his shirt emblazoned No. 3, stands cap in hand facing a three-tiered stadium packed with fans. The photo itself, taken June 13, 1948, is one of the most famous in sports history. But even folks who can't recognize Yankee Stadium would likely guess Babe Ruth. The line of ballplayers off to the side, the bald guys in suits and overcoats, the crouching photographers with flashbulbs — all trigger recognition.

Unknown photographer, "The Beatles, 1965."

Centennial gift

The back photos were a 2015 centennial gift to the museum from Twin Cities collector Howard Weiner. He began his quixotic collection nearly 40 years ago when, in a Jerusalem shop, he spied a curious image of the back of a balding head crossed by the strap of an eye patch. He immediately recognized war hero/politician Moshe Dayan, much as Americans of a certain age instantly know the chiseled head and slender shoulders of President John F. Kennedy.

After buying the Dayan photo on a whim, Weiner began accumulating "this odd and wonderful collection," as David Little, the institute's former photo curator, called it. With the exception of a few art photos such as Robert Mapplethorpe's portrait of a favorite model, most of the back portraits are cultural curiosities rather than aesthetic statements.

They fascinate because they tap into the public's collective memory of their subjects. Viewers bond in shared recognition of the gestures, stance, attributes and attitudes of the people pictured. Or as Little puts it in a catalog essay, "Images are the deep structure of popular culture, producing a kind of knowing that inhabits mind and memory."

Among the hits are the redwood-thick and very creepy neck of boxer Mike Tyson, bare-backed Marilyn Monroe, cellist Pablo Casals playing in a stone tower, architect Philip Johnson in his glass house, and President Lyndon Johnson ruminating in the Oval Office.

Still, fame is fleeting. That nest of beribboned corkscrew curls? The three vagabonds perched on old-fashioned suitcases? The barelegged blonde in the military shirt? The neatly tailored guy pacing with a cane? The bodybuilder in leopard-print briefs?

However famous they once were, only cultural historians or Americans of a certain "maturity" are likely to recognize the backs of comedian Lucille Ball; early film stars Douglas Fairbanks, Mary Pickford and Charlie Chaplin; leggy Betty Grable; President Harry S. Truman, and muscleman Charles Atlas.

And only true fans, or photo hound dogs, will figure out the guy with Brylcreemed hair wearing an impossibly baggy suit in a Richmond, Va., train station. 'Nuf said.

Facing front

Celebrity portraits from the front, like these from the museum's collection, are mostly collaborative efforts in image making. Done right, however, they can be surprisingly revealing, as Richard Avedon proves in 11 images.

All of his subjects — ranging from poets to film stars — are shown full face and alarmingly close up. Comedian Jimmy Durante breaks set in a telltale blur, while Humphrey Bogart's steely disdain stares the camera into submission. Sexpot Marilyn Monroe and former President Dwight Eisenhower, however, seem to have let down their professional guard. As if succumbing to inner demons, Marilyn looks ravaged and "Ike" drifts into an existential void in what is undoubtedly the best photo ever taken of him.

Where Avedon typically shut out everything but the faces of his subjects, Arnold Newman was the master of context. Each of the nine classic Newman portraits in this exhibit use perfect detail to compress a life story into a single frame.

Igor Stravinsky leans on a grand piano whose triangular shadows and swelling lid echo the composer's pose and the angular rhythms of his music. Jackson Pollock stands among a mess of paint pots, a skull behind him eerily foreshadowing his early death. Anglo-Irish painter Francis Bacon glowers disdainfully from the bare-bulb shadows of a claustrophobic space like those in which he trapped his subjects.

Only people who are very brave, unnervingly self-possessed or utterly indifferent dare subject themselves to the scrutiny of a lens as searching and manipulative as Avedon's. Newman was a kinder, gentler and more collaborative portraitist, but equally revealing of the soul.

Perhaps those celebrities who turned their backs to the camera were onto something after all.

mary.abbe@startribune.com 612-673-4431

Twitter: @maryabbe