After witnessing so much sorrow, however, he felt the need for a change of pace and became fired up about his portraits of naked rumps.

These began initially as occasional exercises involving close friends but Cheng took it up in earnest this March when he launched a crowdfunding campaign to raise a modest 10,000 yuan (HK$12,700) by the end of April to help finance his efforts. Conducted through Kaistart, a site run by a Hangzhou-based start-up, the campaign secured 26,786 yuan from 228 backers.

As an incentive for potential models, Cheng pledged to give every volunteer a full-sized photograph of their backside portrait, and that seems to have drawn interest - some from an unexpected quarter.

"A toilet manufactuer from Xian called me the other day and said he'd love to show his rump for my camera," Chen says, chuckling. "If he wasn't thinking about promoting his products, then he must be very curious about what I do and share my attitude to human buttocks."

Of those who have offered to pose for Chen in the past two months, most are younger people, born in the late 1980s or the '90s, who are less inhibited about stripping off for the camera. They include some successful entrepreneurs.

"A young businessman from Chongqing not only wanted me to photograph his buttocks, he also pledged to cover all expenses for future shoots in his city."

But Chen concedes it's a "challenging mission", not least because the Chinese are generally more reserved and cultural norms call for modest behaviour.

"Most people gape at me when I suggest the idea."

But to the photographer, taking pictures of bare backsides is no different from photographing flowers and he seems as much drawn by the aesthetics of human anatomy as he is driven by the notion that buttocks are a "mirror of people's lifestyles".

The typically sedentary habits of city folks would surely mean flabby hips and thighs, just as a sporty person would have better conditioned glutes. So persuading his subjects to get off their chairs and examine a picture taken of their backsides is a way of getting to rethink their way of life, Cheng says.

Born in Lianyungang city in Jiangsu province, he was artistically inclined as a boy and enjoyed writing poetry and painting. As the mainland began opening up to the world, material coming from beyond its borders held a particular fascination, including pop and rock music from Hong Kong and Taiwan.

But what has intrigued him since he was 12 years old were the images produced from his elder brother's camera, a twin-lens reflex model made by Seagull, the oldest camera maker in China. Wherever his big brother went with the camera, Chen would follow, especially since that meant he sometimes got the chance to get some hands-on experience taking pictures.

Standing in the dim red light of a darkroom as a child, the sight of images slowly emerging from blank photographic paper was like magic, he recalls.

His passion for photography, however, wasn't really ignited until he enrolled in the photography department at Nanjing Normal University. That's when he started to appreciate photojournalism.

Mostly influenced by Pulitzer-winning images, Chen and his classmates would travel the country to record everyday life in some of its poorest and most remote areas. They would stage exhibitions of their photos from those trips to help raise funds for rural schools.

"It was only when we were inundated with letters asking for help from ever more poor townships that we sensed the formidable power of photography," Chen says.

He later embarked on a series of photos of Chinese "comfort women", which formed the subject of his first major exhibition in 2002. Since then Chen has been committed to capturing different aspects of the human condition - peasants living in abject poverty, people struggling with chronic depression and so on. Of these efforts, one has left an indelible memory in his mind - his experience covering the massive earthquake in Sichuan province in 2008, which killed about 70,000 people.

"It's extremely sorrowful when you know there is someone buried alive in the debris under your feet, but you can do nothing about it," says Chen.

"The earth was constantly trembling and it's heartbreaking when you have no choice, but to turn around and abandon the survivor."

A photojournalist with , a newspaper in the capital of Zhejiang province, Chen and another reporter arrived at Beichuan, a town close to the epicentre, just two days after the 7.9 magnitude quake struck.

As he kept working in the intervals of calm between the many aftershocks, Chen suddenly heard the clear but feeble voice of a woman from under the rubble, begging for help. She sounded very close but he had no way of figuring out her exact position. Following the sound, Chen stuck a drinking straw through the debris to try to funnel some water to her and quickly emptied a bottle.

Although unable to quell his own fear, Chen urged the woman to hold on and vowed to stay until she was rescued. But it was a promise he could not fulfil - rescue workers and journalists were ordered to clear the area as a nearby landslide lake was about to break its banks.

After 16 days in Beichuan, he returned to Hangzhou a changed man. During his first night back, Chen woke with a start to find himself trembling fiercely. He sat up in bed and started crying like a baby.

"The suffering brought about by the earthquake and my consequent depression is an experience that will never fade from my memory," Chen says.

In February 2009, his photos capturing the all-out efforts by Chinese soldiers to rescue earthquate victims in Sichuan won first prize for breaking news in the prestigious annual awards presented by the World Press Photo organisation in the Netherlands.

But it is still hard to shed the sense of despondency that the experience left him with. For a long time, he tried to avoid looking at pictures of the disaster; if he came across any at a newsstand, the sad memories came to mind and tears started to flow. Instead, Chen prefers to look occasionally at notices that families post of missing persons; that's because those were the only photos from the Sichuan quake where he could see some smiling faces, otherwise it would all be despair and grief, he says.

But after witnessing so many life-and-death struggles, Chen wants to shift part of his focus from people's living conditions to buttocks, a part of the body that's usually hidden from sight.

"Actually, it's not that experimental," Chen says of the project. But his suggestion to newlyweds surely qualifies as unconventional: in addition to traditional portraits in bridal garb, couples could have photos taken of themselves cuddling with their bare backsides.

To Chen's mind, it's a romantic image - one that the couple might hang on the wall in their new home, he says.

Three more top Chinese photographers

The phrase "most sought-after fashion photographer in China" doesn't begin to describe Chen Man, 35, whose images have graced the covers of international glossies such as and

Wherever there were wars, plagues and natural disasters, Tang Shizeng was likely to be found. A senior photojournalist with Xinhua news agency, he covered the first Gulf war and spent three years in Baghdad in the early 1990s when he had the chance to show how communities were made wreteched by the continuing violence. It instilled in him a deep desire for peace and appreciation of life, but Tang paid a toll, too. He suffered bouts of deep depression, and prolonged exposure to radiation in war-torn areas has badly affected his health.