Former Olympic icon turned transgender heroine Caitlyn Jenner has triggered debate about whether there could be a "third gender", American portrait photographer Annie Leibovitz said on Wednesday.
The former decathlon gold medallist is featured alongside the likes of pop diva Adele, Myanmar democracy leader Aung San Suu Kyi and Britain's Queen Elizabeth II in a new exhibition by Leibovitz currently on show in Tokyo.
An out-take from last year's Vanity Fair cover photoshoot features Jenner in a white corset, a shot Leibovitz described as a "tongue-in-cheek" nod to the magazine's arty style.
"What I like about what Caitlyn Jenner has done for us is that she has sort of opened up this whole idea that maybe there's more than two genders," said Leibovitz.
"Maybe it's a little more complicated than we were thinking. There are many parts to gender.
"She had everything money could buy, including the breasts -- she had beautiful breasts."
Leibovitz recalled that shooting the queen had been like photographing an elderly relative, praising the 89-year-old monarch's energy.
"The queen was like everything you would want to imagine," Leibovitz told AFP.
"She didn't get up until I said, 'Thank you, we're done.' Everything I had heard about her wonderful sense of duty was true.
"It was sort of like photographing your great-aunt," she added.
"She was walking up the hall mumbling: 'This is the last time I wear this cape!' It was like 75 pounds (34 kilos), really heavy.
"Of course, I stuck my foot in my mouth by saying 'can you take your crown off?' and she said: 'Can I do what?' She was incredible."
- 'Modern' Empress -
Leibovitz's "Women: New Portraits" opened in London last month and continues a project she began more than 15 years ago.
The 66-year-old unveiled portraits of Pakistani activist and Nobel Peace Prize winner Malala Yousafzai and American Olympic swimming champion Katie Ledecky for the Tokyo leg of the exhibition.
She also talked of wanting to photograph Japan's Empress Michiko, who she described as "quite extraordinary, very modern".
Leibovitz's collection documents women of outstanding achievement and also features photos of Misty Copeland, the first black American prima ballerina, US presidential candidate Hillary Clinton and tennis pioneers Venus and Serena Williams.
"Being a fighter is part of being a woman," said Leibovitz. "Some of us managed to survive."
The former Rolling Stone magazine photographer is arguably best known for her iconic portrait of a naked John Lennon curled up next to Yoko Ono, kissing his wife on the cheek.
The Beatle was shot dead outside his New York apartment building just hours after posing for the photo.
"I was expressly told (by the magazine) not to take that photograph with Yoko," said Leibovitz of the Rolling Stone cover shot.
"But John wanted Yoko in the picture. At the last minute, Yoko didn't want to take her clothes off. John acted pretty normal, but I always felt I didn't really 'get' Yoko at all until after John passed."