Milan Kundera, in his most recent book, "The Curtain," a seven-part essay about the history and art of the novel, talks about a novel's passion "for the mystery of the present moment, for the richness contained in a single second of life," and reminds us of "the existential scandal of insignificance." These three phrases seem to sum up most photographers' concerns as well.

What does it mean to be a photographer? With slight variations we all say pretty much the same things: we wish not just to look but see; we try to enter other worlds even if it is through our navels; and we hope to make a difference.

We are curious and driven, outgoing or introverted. On the prowl—shy, maybe even guilty, about our pursuits, because we know that what we do is not polite. We search for that secret which, like a pearl in the ocean, is not easily found or given up. Our search is about an elusive, slippery moment that is either so striking that it takes your breath away or so deep that it carries you off. A particular moment comes once, and it is so intense that, when it works, what is visible and what is just sensed merge, and an image comes to life on a piece of paper.

In our fragmented, fast-changing, and unsettled world, with its ever-ongoing wars and disasters, with its poverty and suffering, with so many lives and cultures torn apart, these excellent photographers throw themselves into their projects with the passion and energy of youth and give us their perceptions, and in so doing, hope. Some risk their lives or immerse themselves with compassion into complex and difficult situations, as in a photo essay by Rick Gershon about children orphaned by AIDS in South Africa, or in Gina Brocker's photographs of a family of Irish Travellers forced to give up their nomadic lives and leave their traditional campgrounds. In both of these essays, the children in the photographs remind us in their resilience and joy of what really matters.

We see the horror of war in Iraq in the red of blood and the anguish of both soldiers and civilians in Peter van Agtmael's photographs. He says he hopes that they "serve as evidence and reminders of war's wastefulness and its wretched consequences for ordinary people." In another group of pictures, Kitra Cahana pulls us into the settlers' despair and their futile fight to keep their homes and community in Gaza. As a rabbi's daughter, she sees her photojournalism as a vocation and part of her Jewish tradition and wishes to be "a light unto the nations" and to practice "healing of the world."

When we document life in front of us, what we end up with is not the truth but a photographic reality. Honest yet subjective, each of us, with our own approaches and perspectives, creates a memorial to a particular instant that passes in a blink of the eye, like the "equivalents," the cloud pictures, of Alfred Stieglitz.

Some of the photographers are interested in echoes of the old or a search for the new and investigate family and transition. Irina Rozovsky calls her intimate portrayal of home and relatives a "blend of fact and fiction . . . a drama," and Beatriz Wallace, after leaving New Orleans in 2005, finds doppelgängers of her family along the river in Columbia, Missouri. The passage from childhood to adulthood is recorded by Elizabeth Looke-Stewart as she tenderly watches her four younger sisters' transformation. In set-up portraits of himself in pretend relationships with strangers, Futoshi Miyagi looks for connections as part of his "elaborate coming-out plan," but he remains alone, as do his partners.

Cartier-Bresson said he smelled a picture. For Mario Giacomelli photography was a necessity. "I look for something that moves, but more for something that moves me. I look for what is invisible: an essence or a ghost. Sometimes I know I have gotten a picture because I blush or hear a sound in my head, like a hum, and because when I press the shutter, I can breathe again."

Every photograph is unavoidably a representation of something that no longer exists. Greg Mrotek writes, "A vacant room is a blank canvas on which we can draw our lives," and in a picture below a blue sign reading Frozen Foods, he shows us a row of moldy stains, the breath freezers left on the wall. In another one of the introspective reveries about earlier times and abandoned spaces, Lissa Rivera sees prep schools empty of people as halfway houses between boredom and anticipation.

And then there are Ami Howard's sheet people, not exactly past but fantasy—pseudo-ghosts who float through public places seemingly unnoticed, but who, like artist Christo's wraps, add whimsy and mystery to what they touch.

Photography is a journey—alone in silence, swimming with currents, we wait for revelations. We chase our luck; we forget who we are; we find our courage.

While some look back and others step into the unknown, a few prefer to linger and feel the beauty of the moment. Adam Kuehl traces Savannah in the late evening, showing the misty majesty of nature and the outlines of man-made structures. Elizabeth Claire Rose goes close and finds epiphany in the glow of stray plastic among the weeds. Her color photographs show collisions of the synthetic and the natural world that are made to glitter by sun and ice.

Kathryn Parker Almanas's still lifes are of mangled pastry and red-dripping jelly on hospital trays and inside specimen vials. These images were triggered by her own serious illness and are a study of mind distortions that lead us into confusion about food and bodily fluids – in her words, to "explore the dual nature of the things we desire, the unknown."

For Kim Badawi, photography is storytelling. He likes "to work with performers and illusionists," and follows a male construction worker who becomes Celeste in her nightly retreat into sex and fantasy. In "Illusions of a Glittered Life," he gives us in both pictures and words, a moving, powerful, theatrical story of a pathos-filled life.

Too often, in the service of politics and commerce, photographs are inadequate or false. But here, we can project ourselves into these images filled with insight and compassion and enter their collective memory as a continuation in the history of photography. Each of these photographers, in their own perceptive way, surprise us with their finds. They carry us along on their journey, and with their eyes turned both inward and out, they become barometers of our time.