Their faces emerged from boxes that had been packed and stored out of sight. Some, including those of children, had plastic bags over them. But when New Zealand photographer Fiona Pardington first encountered the plaster cast heads, including some of her Ngai Tahu tipuna, she knew she could not think of them as mere objects.

"I tried to treat them with the same respect as any individual," says Pardington, chatting at a restaurant not far from her home on Waiheke Island. "I decided long ago I was going to treat them as portraiture rather than still life."

The plaster casts were created in the 18th and early 19th centuries when European explorers sought to find a means of documenting all that they encountered. This was before photography was invented, when phrenology, the study of people's skulls, was prevalent. From 1837 to 1849, French explorer Dumont d'Urville took an ambitious voyage around the Pacific, taking with him an eminent phrenologist, Pierre-Marie Dumoutier, to preserve likenesses of people.

Pardington has photographed a series of the casts, and the results are so life-like they send a chill down the spine. The images are part of her new book The Pressure of Sunlight Falling, and although they are essentially plaster moulds, Pardington couldn't help but feel some were "more present" than others.

The Govett Brewster gallery in New Plymouth is holding an exhibition in association with the book, the latter a collaboration with her brother Neil Pardington, and editors Kriselle Baker and Elizabeth Rankin. And while the photographer is quick to point out that this is a collaborative effort with her contemporaries, it is also a homage to the work of D'Urville and Dumoutier.

Even so, the casts' spooky realism is largely thanks to Pardington's precision behind the lens, her attention to framing and light. The title of the book was inspired by a BBC documentary about a Japanese spacecraft, propelled by the pressure of sunlight falling on large solar sails. It struck Pardington that something so minute as light particles could have such a powerful impact.

Kriselle Baker, who accompanied her to one shoot at the Auckland War Memorial Museum, writes of how tragic the heads appeared before Pardington weaved her magic, using just the ambient light in the room to bring them alive.

Pardington was in Wanaka several years ago with historian and Ngai Tahu representative Tahu Potiki, when he mentioned to her there were tipuna in the Musee de L'Homme in France. She knew she'd struck upon something important, and soon embarked on a project that would consume her for four years. Pardington had also seen a lithograph of two 19th century life casts in an auction catalogue. She travelled to France several times, as well as to the Auckland War Memorial Museum, to photograph more than 50 casts of Maori, Pacific and European heads, including some of her Ngai Tahu ancestors.

"It's bathed in an ancestral light and the whole idea of belonging and sitting well with meaning in your own life, that's something we all want."

There is perhaps no one better suited to photographing the casts than Pardington, one of New Zealand's most lauded photographers. Throughout her career she has displayed an interest in psychoanalysis, memory and history, receiving many fellowships, residencies, awards and grants along the way, including the Ngai Tahu residency at Otago Polytechnic in 2006. Yet for a long time Pardington felt hesitant about acknowledging her roots. She alludes in the book a difficult childhood as part of the reason and because, she says, she doesn't look particularly Maori.

"I was afraid of not being accepted but at that time I didn't realise if you have whakapapa it's completely inalienable from you. Ngai Tahu just said, we know exactly who you are, we know who your family is. Welcome."

This led to her ongoing fascination with her familial and spiritual past, including her well-known series of evocative photographs of ancestral greenstone "heitiki" photographed from the collection of Auckland Museum.

The cast project also appealed because of the parallels between phrenology and photography, the latter eventually rendering the former redundant. Phrenology was the practice of examining a person's skull to determine what went on inside their brain, a practice eventually derided as quackery. Many casts of important people at the Musee de L'Homme were mixed up with casts of criminals and the criminally insane.

"It's the Hello! magazine of the 18th century, used to study criminality, teaching, you name it, everything you can think of that has been photographed used to be cast," says Pardington.

Curiously, the book coincided with the evolution of Pardington's practice, as she moved from analogue to digital. That made the actual photographing of the casts unnerving, she says, because it was so quick.

Contacting the Ngai Tahu family had its own challenges too, as she had to convince them the book would not be exploitative.

"You can't take this for granted because these are real people and they would've felt really strong connections with us," she says of the casts. "That in itself is something important.

"Whakapapa can't be alienated from any individual and it's not something you have to earn, it's the essenceness of any object like that."

It's worth noting how chiselled and good-looking many of the men are. Back then toil was tough and fast food non-existent. The impressive cover image is of the tattooed Matoua Tawai, a mysterious figure believed to have come from Northland. Many of the men cast were respected leaders. Piuraki, also known as John Love Tikao (Ngai Tahu), became a taiaha specialist who joined a whaling boat and sailed to Europe. He spent years in France and England and is said to have spoken seven languages.

"These people were phenomenal," says Pardington. "They had to be expert orators as well as top athletes and war strategists. It's easy for us to underestimate the standing of these people."

The notion of preserving faces as representatives of a foreign culture would perhaps not be deemed politically correct today so it's intriguing to think how Dumoutier approached his subjects.

They had to be convinced to sit for hours as the claustrophobic plaster covered their faces, straws sticking out of their noses to allow them to breathe. One subject in the Solomon Islands became so distressed during the process, he ran off and banged his head against a tree to free himself from the plaster.

There are several essays in the book, providing fascinating insight into the past.

Producing the book was a long-held ambition of Pardington's, not only to work with her brother but to collate her work into a form that allowed for intimacy, the chance to pore over the pages rather than glimpsing them in an exhibition. She also hopes it will inspire people to research their ancestry and to discuss the ideas it brings to the fore.

"To me, these are incredible treasure troves of knowledge and knowledge systems and people's aspirations. In the case of D'Urville and Dumoutier, those collections represent traces of their entire life's production. So that in itself is very special and beautiful. Even if some of it is crazy."

Book: The Pressure of Sunlight Falling by Fiona Pardington, edited by Kriselle Baker and Elizabeth Rankin, Otago University Press, $120, released on Monday

Exhibition: The Pressure of Sunlight Falling

Where and when: Govett-Brewster Art Gallery, New Plymouth, to August 28