During the summer of 1937-38, at Culburra Beach, Dharawal and Dhurga Country on the south coast of New South Wales, a young man emerges from the surf and lies face-first on the sand. His friend, who is holding a Rolleiflex camera, exposes two negatives, one of which he’ll dismiss due to technical inadequacies.

Decades later, this image will be considered the most iconic photograph ever taken by an Australian. It will also be the most printed.

For many, Sunbaker (1937) sums up this nation’s obsession with beach culture, in all its relaxed and hedonistic glory. The photographer, Max Dupain, would eventually claim that he didn’t want to be defined by it, awkwardly stating that he was “embarrassed by all the attention it was getting, from jingoistic Australians … and from gay couples decorating their new flats.” Regardless, in 1992, after Dupain’s death, a critic wrote: “[His work is] so quintessentially Australian that it would be almost unpatriotic not to like it.”

Dupain’s reservations about Sunbaker are understandable, considering he was a momentous force in Australian art photography over five decades. His practice encompassed landscapes, street scenes, nudes (mostly women), advertising, and still life work. In terms of architecture, Dupain was the photographer of choice for luminaries such as Harry Seidler and Glenn Murcutt. For those who look beyond Sunbaker, it’s possible to be awed by Meat queue (1946), in which a group of women line up in a Sydney butcher’s shop when rationing was still in place, and Landscape by night 1, Castlecrag (1980), an image that evokes this continent’s great geological story.

Who was the man behind the art? And who is best placed to unmask him?

The answer to that second question is Helen Ennis, Australia’s pre-eminent writer about art photography. Ennis was formerly curator of photography at the National Gallery of Australia and director of the Centre of Art History and Art Theory at the Australian National University. Importantly, she wrote an award-winning biography of Olive Cotton, who was a childhood friend of Dupain and later his first wife. Even though she was an accomplished photographer in her own right, producing Teacup ballet (1935) among many other wondrous works, Cotton’s career was overshadowed by her husband’s.

In Ennis’s hands, Dupain emerges as a very Sydney artist. He was the only child of Ena, a homemaker, and George, who ran a gym and promoted eugenics. It was while attending the elite Sydney Grammar school, where he didn’t excel academically, that Dupain developed a love of photography, which he shared with Cotton, especially while holidaying together at Newport on the northern beaches.

It’s obvious that Dupain was a highly cultured man, maintaining a lifelong obsession with Beethoven and DH Lawrence. He also adored poetry, considering it a way of being. During the second world war, Dupain worked as a camoufleur – a designer of camouflage – but, holding pacifist views, he was uncertain about his contribution. In his diary, he wrote, “… the war goes on bloody and never ending, political strife, propaganda, deceit, hypocrisy, hate. No love, no kindness … How can a man’s ideals survive in this world?”

After the war, and once his legal union with Cotton ended, Dupain remarried, this time to Diana, who was 10 years his junior. The couple started a family and built a house in the art-and-design enclave of Castlecrag, on the northern side of the harbour; Dupain took the opportunity to photograph every aspect of the construction process, including documenting the builder’s mistakes.

Despite Ennis’s extensive research, informed criticism and compassionate generosity, Dupain remains a perplexing character. Indisputably talented and hardworking, he was also an Australian male of his era, in that he felt he needed to be in control or he would be considered emotional. This was abhorrent to him, which was at odds with his insistence that art must be about both the head and the heart.

Tellingly, Dupain is quoted as saying about his childhood: “I was a very sensitive creature. School was a sudden awakening. There were kids by the dozen, malevolent creatures, and only one thing mattered: survival.”

In this thoughtfully structured, readable and in many ways moving biography, Dupain ultimately comes across as someone who spoke against his myth, but also traded on it until the end. He sought out love and intimacy but damaged his family by assigning the copyright for his non-commercial work – that is, his most revered photographs – to Jill White, his longtime studio manager, because he trusted her, and she needed the money (no romantic reason is implied).

Together with Olive Cotton: A Life in Photography, Ennis’s biography of Dupain forms a major study of what is arguably the most significant period of Australian photographic practice. Eschewing gossip and speculation, Max Dupain: A Portrait focuses on the work, which, when considered as a whole, is diverse, brave, not always successful, but yearns for something that might be considered the truth. It isn’t all about a young man lying face-down on a beach.

• Max Dupain: A Portrait by Helen Ennis is out now (Fourth Estate, $55)