One aspect that has prevented many women from jumping on the bandwagon is privacy - and the potential danger their photos could fall into the wrong hands.

"What if they are leaked?" said Wu Xia, a 22-year-old sales clerk at a multinational consumer goods company in Wuxi, Jiangsu province, who was clearly appalled at the idea of posing for nude pictures.

Although photographers naturally own the creation rights of their work, under Chinese law customers own the portrait rights of such photos, which means if the images are distributed by studios they will face legal penalties.

"Also, charges over pornography (illegal in all forms) would be inevitable if the photos were posted on the Internet," explained Shi Yu, 50, a photography expert and deputy director-general of the China Association of Social Workers' committee of wedding service industries.

To put customers at ease, studios often sign confidentiality contracts that promise whopping sums of money in compensation should the photos be improperly distributed.

"We'd be in big trouble if the photos got out, not only legally but our reputation would be severely damaged," said Ou at Dayu Photo Studio. "We want to get more business in the future, so we're not going to put our neck on the line like that."

She said staff members do all they can to ensure clients' privacy, explaining that the retouching of photos is always done in a private room, while software installed on the computers monitor and record the use of any flash drives or other "removable discs".

"All photos are deleted from the computer in front of the customers as soon as they are given their copies and all samples used on the website are with customers' permission," added Ou.

There are no laws or regulations concerning nude art photography or the qualification of a studio to provide the service, according to legal experts. That means, as long as businesses do not violate public order, the pictures are acceptable.

However, as Wei in Shanghai pointed out, contracts and strict company rules only prevent gentlemen, not villains.

"It's our duty to remind young people that we live in the digital age," added Yi Shenghua, a lawyer at Beijing Yingke Law Firm. "They should be clearly aware of the potential hazards."

Trouble for teens

Nude portraits, as an artform, are permitted by the central authorities. Yet, some social analysts claim the new trend for photos among young people is moving away from artist creation and into "unhealthy" commercialization.

In the past, photographs and drawings of naked women could be viewed only in galleries and public exhibitions. Today, albums of the pictures can be bought at markets.

"Nude art is at risk of being misused in commercial circles," said Wei Pishen, 54, chairman of the Shanghai Photography Trade Association.

"So, if photographic art is becoming a business service, that could cause trouble."

The changes in social values and sexual liberation that nude photo shoots are said to represent could also hinder the development of teenagers, according to Xia Xueluan, a professor of sociology at Peking University.

"Juvenile crime has continued to worsen, especially sexual crimes, to which the open-mindedness of the public and the easy availability of scantily clothed men and women both make great contributions," he said.

"In primitive times, people knew to cover their bodies with leaves. Why are people now taking off their clothes? How can youngsters cast aside etiquette and shame?"

He Lina in Shanghai has a daughter in her 20s. In her bedroom hangs a picture of her playing tennis in a gymnasium, her hair in braids, which He thinks is the right image for teens to learn from.

However, photography expert Shi Yu argued people like He and Xia are simply trying to hold back history.

"Three decades ago, many things we are doing today were prohibited. Who is to say what will be acceptable in 10 years?" he added.