Traditional media continues to atrophy, but the need for content has not. If anything, there is a greater need for content than there has ever been. Columnists talk about the death of newspapers, but we are all reading more text, viewing more images and watching more video; we just happen to be doing more of it online. Talk to anyone under the age of 30, and chances are that they read few, if any, print publications.

It has become harder to make a living as a photographer, but easier to sell photographs. Online distribution has made media more easily available, but more media now sell at commodity prices. Photographers are no longer paid simply to make a technically competent photograph. Kodak roll cartridge film and Polaroid instant film popularized photography, but it is digital photography that has put the skills of making and developing properly-exposed photographs into many more amateur hands. That has caused deep concern among many aspiring professionals, who find themselves in an arms race with affluent consumers to buy more and more expensive equipment. The price of stock photographs has been driven down to the cellar; microstock photos sometimes sell for as little as a few dollars, or even a couple of dimes. Robert Lam got $30 for a Time magazine cover photo.

Professional photographers used to be able to count on residual stock photo sales. The amounts could be slight, but, given a decent-sized library of photos, the sales could accrete to respectable totals over many years. Professional photographers could count on their privileged access as proven alchemists in the photochemical trade, the arcane incantations of silver nitrates and bromide, the calculus of F-stops and apertures, to which only the most dedicated amateurs were willing to apprentice.

A look through the historical list of photography's Pulitzer Prize winners shows that there has been a rich tradition of amateurs who have captured what have become momentous, iconic photographs. Virginia Schau, for instance, covered a rescue on Pit River Bridge and won the 1954 Pulitzer. Jacque Henri Lartigue's wealth gave him the leisure to make a name for himself and his race car photographs. Apart from such notable amateurs, however, until the advent of digital photography, marketable photography, especially, assignment photography, was the purview of professionals.

The digital darkroom has democratized photography. Anyone with a computer can develop photos with equipment that has become affordable to an array of photographers. The traditional "wet" darkroom could be unforgiving: set the wrong temperature or mess up the timing, accidentally expose the film to light, and it was possible your images could be lost to posterity. Even the professional was not immune, for instance, when several rolls of Robert Capa's photographs of D-Day were lost to a technician who melted the emulsion (the accident created the blurry, graininess of the surviving images that cemented them as icons).

Every generation has its own icons. "Across the generations, one picture supports another picture, and a lot of icons have that kind of power, they relate back," says Hal Buell, the former Head of the Associated Press Photography Service. Henri Cartier-Bresson was inspired by the Parisian scenes of Eugene Atget, and he, in turn, inspired an entire generation to look for "decisive moments." (Several of the photographers in this book count him among their idols.) Cartier-Bresson not only changed how we thought of picture making (how many serious photographers have not read his book The Mind's Eye?), but his simple act of carrying and using the rangefinder, a small and quiet camera effective for surreptiously capturing people in unguarded moments, changed how we would view the photographer as narrator. Technology made the camera lighter and more portable, and altered how the Photographer could capture his scenes. No longer would he have to wait—as Matthew Brady and his men did during the American Civil War—for a battle to end in order to depict its carnage. Now like Cartier Bresson, the Photographer could capture images as he came upon them, unexpectedly. Like Eddie Adams at the execution of a suspected Viet Cong combatant, or Larry Burrows during a helicopter evacuation in Vietnam, he could insert himself into a scene. Eugene Smith could hunt his stories of a small Spanish Village or startle us with his images of the mercury-poisoning at Minamata. (Some of us even forgave him for how he manipulated his scenes, as he did, when he repainted the eyes of a mourner at a wake.) City scenes would become landscapes, as they did when Andre Kertesz depicted Washington Square Park. The Photographer could turn the camera on himself and his friends, as did Larry Clark, or make it part of his own personal journey, the way Robert Frank did when he traveled across America. These idols had in common that they were not just technicians (though they were nearly all masters of their equipment and craft)—they had subjects over which they obsessed and had strong personal views they wanted to convey.

More than ever, personal voice has become important for the media artist who wants to stand out, convey a message—maybe even still make a living. How does one do that these days? Magnum photographer David Allen Harvey says that a key is deciding what kind of lifestyle you hope to lead and the consequent overhead that choice implies—that determines the number of commercial projects you need to pursue to subsidize your personal, less lucrative projects. Critically, you also need to develop a unique voice. The author John Gardner once said he was startled to learn how many of his writing students wrote as capably, even beautifully, as he did. He knew that he would have to explore styles and themes that they would either be unwilling or incapable of exploring. Andy Levin says doing his Coney Island project for himself allowed him to explore different techniques.

"Concentrating on a long-term, deeply felt project is the best way to establish yourself as an original photographer with something to say, and though it take years to achieve decent results the wait is usually worth it," says Jon Anderson. 

Traditionally, the horrors of war or privation provided this fertile ground for many photographers. "I always understood the function of being a photojournalist as a go-between, shuttling between one group of people and another to try and explain how the others are faring," says John Vink.  Yet years of war photographs and countless images of starving refugees have caused writers and photographers to wonder if we have become hardened to those horrors. Susan Sontag would disagree that this should immunize anyone from the horrors depicted by our war correspondents or the sorrows of those caught up in crises. Photographers like Sebastio Selgado have been accused in essence of cataloging the poor and downtrodden, stripping them of context and individuality, to the point that others become blinded to them. That Salgado has also been a pioneer in finding new venues and sponsorships for his work, (for instance, the sponsorship of his exhibit In Principio by the coffee maker Illy), walking that fine line with commerce with which many artists and critics have long been deeply uncomfortable, has not helped that particular aspect of his cause either. "I do a lot of work just to earn a living," Salgado explained to The Times (UK). His work speaks for itself, however, and he is hardly the first or only photographer of renown who plies commercial photography as a trade. As Michal Heron notes, "the lines between commercial and assignment and fine art are so blended as to be indistinguishable."

Of course, voice needs its metier. Photographers need to find their passion, the cause or subject to which they want to devote their time and effort. Those themes can be grand: love, war, hate, humanity, and though some veins have definitely been more exhausted than others, there are lodes to mine for those willing to push the envelope.

"The most important type of immersion required for a project is the mental kind," says Jason Pagan. "A fixation, obsession if you will, is required with the subject, the images, and the need for the project. Physical and logistical immersion is wonderful when you have it, but mental immersion will see you through even if you have to go back time-and-time again to get the story told."

Diane Arbus brought us her freaks and grotesques. Cindy Sherman parodies herself through different guises, acting out different archetypes, as she questions the nature of narrator and subject—we wink at the joke and think both her and ourselves clever. Maybe the subject matter does not need to be so exotic. Sally Mann has long been effective as a photographer, because she uses what seem at first to be familiar subjects: her exploration of her family, for instance. (Her daughter Jessie Mann now explores being both a (well-known) muse and an artist.) We see how Mann sees them: young and feral, or still and already full of the wisdom into which we know they will grow. In her early photos of her family in Immediate Family, we see hints of the themes that emerged into her later works. When her children were young, they were forces of nature. We follow her husband as he faces the weight of a degenerative muscular disease; once a virile man, we see how the force of nature falls on his shoulders. Her work on the decomposition of bodies, and on her study of the form of trees has become a natural extension of her life's work. Mann's eye is unerring, keenly focused on finding that life force in our forms. What makes her a master is how she reinvents herself in the actual forms she studies, and the point in the cycle at which she studies them, but she has always returned to find what it is that is "alive" in each of us, and what happens to us when it is gone.