Photographer Eve Arnold once wrote of being a member of the illustrious photo agency Magnum: "It's like being part of a family. You love all of them, but you don't like all of them. It's an organic thing." After 60 years in existence, the Magnum "family" is still producing some of the world's finest photography. To mark this milestone the agency has, in typical fashion, offered an entirely appropriate celebration in the form of its latest retrospective, Magnum: Magnum.

Born in 1947, Magnum was founded by four very different photographers, Robert Capa, Henri Cartier-Bresson, George Rodger and David Seymour. However, they shared a common desire to create a new agency, owned and operated by photographers: its purpose, to document world events and issues and show the photograph to be as powerful a method of journalism as the word. It would also provide an invaluable historical archive.

Unique in concept and philosophy, Magnum's relevance was soon recognised. New members were chosen only by existing ones, under rigorous application processes designed to ensure the agency's ethos remained intact. This approach has ensured that, today, this collective of international proportions and generational diversity continues to bring us iconic and beautiful photography.

The 60th anniversary is being marked by the production of a new book. Upon a suggestion from another Magnum stalwart, Martin Parr, each of the agency's photographers were paired with a fellow member who would select the other's work and pay written tribute to the person and their photographs.

Like most families, Magnum shares its own dynamic and not everyone gets along all of the time. Recognising this and calling on the expertise of publisher Thames & Hudson, who understood the delicate balance, the collaboration has resulted in a collection of work, simply and immaculately presented, which feels fresh despite being garnered from an existing archive of renowned images.

While it may be true that a picture is worth 1000 words, it is the insightful and at times moving accompanying texts - edited extracts from which are included on these pages - that really gives the book another dimension. What the whole also offers photographers is the rare and invaluable experience of allowing their work to be edited and critiqued by their peers. The result is as fascinating for us as it may be terrifying for the subjects, as evidenced by one member who, when asked what it felt to be edited by his contemporaries, replied: "Russian roulette."

If Magnum is a family - or dynasty - there is no disputing it is a big one. Even the agency's name, a word itself big in suggestion and definition, is synonymous with photography, to the extent that the book needs no subtitle. The reflection of the agency's name in the title - Magnum: Magnum - hits on another powerful message of the book. Magnum, like most 60-year-olds, has matured and feels the need to reflect. The big ideas, commitment, respect and passion are packaged in a book that is so physically large you will never really want to carry it around.

No matter: even after one reading, the power, beauty and relevance of the images endures. They imprint themselves on our individual consciousness and on our collective cultural landscape, to be carried with us at all times. Henri Cartier-Bresson

By Eve Arnold

(Opening photograph: Muslim women praying at sunrise in the Himalayas, Srinagar, Kashmir, India, 1966)

I once described Henri Cartier-Bresson as "the poet with the camera". From him I learned the need to try to tell an entire story in a single definitive image. I knew HCB since 1954 and he never failed to surprise me. Hanging in my drawing room is a photograph that he gave me of women praying at dawn, waiting for the sun to come up - and as far as I'm concerned it's the best picture he ever made. It's unexpected, symmetrical and just does something to you.

The cramped and badly equipped Magnum office was filled with photographers and enthusiasm. Cartier-Bresson would be looking at our pictures. He would hold a print upside-down and talk about its merit. His judgement was always to the point: direct, thoughtful and fair. Thomas Dworzak

By Larry Towell

I chose these pictures (including Russia, February 2001, above) because they make me think of something other than what they are, something universal and so common that I have seen them in my own back yard.

These pictures are not poetry and Thomas is not a poet. He's a journalist. Yet there is something in them that speaks to both identities.

When Thomas was 20 he moved to Russia to learn to photograph. Since then he has documented most world tragedies from Bosnia to Chechnya, from Iraq to Palestine, and from Afghanistan to Haiti. Yet he has not hardened his heart, as do many of his colleagues, because, in the cobweb of political deceit, he manages to find the universal seed of truth.

These photographs remind me that a photographer can redeem his own existence, and the existence of those around him, by observing small beauties and small hopes in these dark and appalling times. W Eugene Smith

By Steve McCurry

The first time I saw W Eugene Smith's photographs was in a fine art photography class in college. As we worked on our own pictures in the darkroom, we talked with awe about Smith's legendary obsession for perfection, which drove him to spend long days in the darkroom. His drive and idealism fascinated me.

During his coverage of the second world war, he was severely wounded while on the east coast of Okinawa photographing an essay titled A Day In The Life Of A Front Line Soldier. He endured two years of hospitalisation and plastic surgery, and commented later that it was his policy to stand up when others were down, and that he had forgotten to duck.

The images selected here represent Smith's unique ability to combine the eye of a photographer and the attitude of an artist with raw honesty and uncompromising integrity. All photographers, in one sense or another, are heirs to his legacy. Chien-Chi Chang

By Bruce Davidson

I got to know Chien-Chi Chang at a small dinner party given in his honour by a New York Times photographer. He stood there quiet, self-composed and observant, like a photo-Buddha, but not with a protruding belly. The gathering was held in a walk-up apartment in what is called "Chinatown". I never felt comfortable with its designation because it denotes the "other". Chinatown is thought of as a place of secrets, suspicion and strangeness. Actually, it is all of the above, but it is also a place where Chinese medical doctors practise, of store front shops with goods from Asia, neighbourhood schools, and families surviving and thriving in a New York City community that is vibrant and visually interesting.

It is where Chien-Chi Chang explores aspects of the culture and the people living there. He uncovers the idea of Chinatown in a way that is both lyrical and poetic. This is not an easy thing to do when people may be illegal immigrants, suspicious of outsiders, or where taking an image may be frowned upon for spiritual reasons. I think of his image of a man sitting on a "flop house" fire escape in the dog days of summer (pictured). He is in what appear to be his underpants. He is taking in some fresh air and a sense of his own freedom high above the teeming streets. It would be interesting to know how Chien-Chi found his way into this tenement and gained the trust of its inhabitants.

Chien-Chi seems to connect to alienation and isolation. His photographs put the viewer into a powerful confrontation with the subject that is visually innovative.

Chien-Chi Chang's inner eye goes beyond today's edicts of the media. One will not see sound-bite, fast-food photography in his work. He takes on subtle and difficult subjects that often go unnoticed and brings to light a vision that is passionate, penetrating and profound. Certainly, we can all learn from him. Abbas

By Jonas Bendiksen

I am a non-believer. Unless I find convincing proof of the existence of God, I will live the rest of my life as an atheist. I believe that unless humankind adopts rational thinking on an unprecedented scale, we are in for big trouble over the coming century. This is why Abbas is such a fascinating photographer. It is hard to find any other who has more diligently sought out religion in all its forms, sizes and colours, and documented where it intersects with culture and conflict. Year after year since the 1970s, he has traversed the planet, bringing back critical images from the ranks of the faithful. One of the most alluring images for me is one from Afghanistan: the Islamic fighter looking out of place. Despite the bemused gaze of the subject, the image is still perfectly tender and respectful: a treacherous tightrope walk Abbas has performed for several decades. Thomas Hoepker

By Paul Fusco

When I look at Thomas's photographs I strongly feel the presence of someone who has brought me into his world, a friend guiding me. I feel the compassion and empathy of this strong and gentle man who has travelled through much of the world to revel in the discovery, understanding and photographing of life with a vision that is broad and encompassing.

He shows the desires, yearnings, fears, triumphs, loves and fantasies of the human being. He is a master of the language of photography and uses it with the insight of a Renaissance painter. His pictures compel us to evaluate life that he has come upon in his wanderings, and preserve it for all to see, feel and ponder.

Thomas has seen much, cared much, loved much. He throws a great long swath of life before us.

MAGNUM MAGNUM PUBLISHED BY THAMES AND HUDSON £95