With many travellers surreptitiously snapping photos of locals without their permission -- or even knowledge -- what is the most appropriate way to get that perfect shot?

To capture a sense of life in a new destination, many travellers have used zoom lenses and hidden-camera tricks to surreptitiously snap photos of locals without their permission -- and likely -- without their knowledge. But approaching photography like a covert operation is not the most ethical way to get a great shot.

Paul Berger, professor of art at the University of Washington School of Art, said a good rule of thumb is to “assume you’re being seen and act appropriately”.

 Appropriate behaviour can be as simple as making eye contact with someone, showing your camera and making sure the person knows he or she is being photographed. If people don’t want their picture taken, they’ll probably tell you by looking away.

“Err on the side of being overly sensitive to people’s feelings,” Berger said. For instance, tourists visiting a cemetery or religious site may want to take a photo of someone in a clearly emotional state. But Berger said a great evocative shot can cross a personal boundary. “Photographing the religious site or memorial itself is ok, but not photos that centre in on an individual,” he said.

But sometimes travellers forget basic etiquette when in a foreign culture – or it goes out the window when trying to take a perfect photo. “There are more problems, I think, with people objectifying people [when travelling abroad],” said Lisa Helfert, a photographer from Bethesda, Maryland.  Locals in poverty-stricken areas can sometimes feel like they’re on display for traveller’s photos, a criticism levelled at operators of so-called slum tours.

Muriel Hasbun, chair of photography at the Corcoran College of Art and Design in Washington, DC, said she tells her students to “treat everyone with respect and care”, explaining that both a portrait of someone and the experience of taking it are more meaningful if it’s a collaboration and a rapport is established. “Common-sense rules of social interaction and consensual types of exchanges are ideal and usually more rewarding to both parties,” Hasbun said. “One learns about a culture and a new place by meeting the people that one finds along the way.”

Tourists are also bound to be confronted by requests for money. There are many sites where “there is a tacit understanding that ‘picture opportunities’ are for sale,” Berger said. But if it’s not clear that this is a standard picture-for-a-price situation, then travellers need to think before snapping their cameras. “Again, the golden rule: would you be comfortable if someone asked you to pose for a photo?” Berger said.

Many times, children are the ones offering a photo of themselves for a small sum of money, having learned from picture-hungry tourists that they can easily sell a snapshot. But ideally, travellers should ask for a parent’s permission – just as they should ask permission of an adult who is about to be the focus of a photo.  And it can’t be a quick question and then a dash to the next willing subject. “When someone is projecting that they’re a guest in your area … if that’s kind of sincere, I think people generally respond,” Berger said. “But if you’re burdened with camera gear and breezing by, people pick that up of course.”

Lori Robertson writes the Ethical Traveller column for BBC Travel. You can send ethical dilemmas to bbcethicaltravel@gmail.com.