MADRID.- “No foto!” was long the refrain from guards at the Reina Sofía museum in Madrid if a visitor dared to attempt to take a picture of “Guernica,” Pablo Picasso’s 1937 antiwar masterpiece. But as one couple took a selfie Wednesday and another woman adjusted her hair while smiling shyly into her phone’s camera, those guards were relaxed, offering tips about audio guides rather than yelling.

The museum lifted its longtime ban on photos of “Guernica” this month, belatedly joining the Instagram era. Still prohibited in Room 205.10 are the use of flash, tripods and selfie sticks, out of concern that the 25-foot oil painting could be damaged.

“Allowing photographs to be taken of ‘Guernica’ is intended to enhance the experience of viewing the painting, bringing it closer to the public and allowing what has been possible in other museums for a long time,” a Reina Sofía spokesperson wrote in an email.

The spokesperson added, referring to advances in technology, “The fact that the means have advanced and that they do not endanger the work did not justify, at this point, the prohibition.”

Ten minutes after the museum opened its doors Wednesday, about a dozen people gathered in front of “Guernica.” Many stood close to the painting before shifting away for a different perspective.

Ronny de Jong, visiting from Rotterdam, Netherlands, spent about 45 minutes taking in the work, a black-and-white cubist painting that depicts the horrors of the Spanish Civil War and disturbed those who saw it at the 1937 World’s Fair in Paris.

De Jong said he loved to remember his museum visits through photos and that he was slightly annoyed that the nearby Prado museum, home to many of Spain’s most important pre-20th-century artworks, banned photographs altogether.

“I did make some pictures — like stealthily — and no one was harmed,” he said.

Another visitor, Flavia Morelli of Rimini, Italy, praised the Reina Sofía’s recent decision to allow photographs of “Guernica.” “I think it’s a way to create a stronger link between people of varying levels of culture and art,” she said.

The Reina Sofía did not explain the origins of the ban on photographing one specific painting, but museums have long struggled with how best to conserve artworks and manage resources while trying to remain relevant to the public. For example, visitors cannot take photos inside the Sistine Chapel in Italy, and photography and filming are prohibited in some special exhibitions at museums because of copyright or lending concerns.

Nina Simon, the author of “The Participatory Museum,” said one reason museums originally banned photos was a fear that people would not visit in person if they were able to see the images online. That worry has abated, she said, but there is still genuine fear that works could be damaged by distracted visitors, and that their photographs could fundamentally alter museum programming.

“There becomes a concern that the museum becomes the backdrop to your perfect Instagram life,” Simon said, “or that the museum shifts the design of exhibits to cater to create great Instagram moments, which could be seen as cheapening in some way.”

Along with the vocal guards, visitors to the Reina Sofía have traditionally been separated from “Guernica” by a long divider that spans the length of the artwork.

But the painting, which Picasso lent to the Museum of Modern Art in New York for decades while Gen. Francisco Franco was in power in Spain, has not always been so restricted. When it was on view at MoMA in 1974, Tony Shafrazi, an artist who later became a successful art dealer, sprayed “Kill Lies All” in red foot-high letters on the canvas.

The painting, which avoided permanent damage because of a heavy coat of varnish, was returned to Spain in 1981.

Seema Rao, who leads Brilliant Idea Studio, a firm that focuses on museum experiences, said museums must learn to keep up with the demands of visitors who have traveled from around the world to see works like “Guernica.” “If you can’t hold on to that, it doesn’t matter, it doesn’t feel like it has value,” she said.

“Museums are basically becoming dinosaurs,” Rao continued. “They are so behind the times. In order to be a part of society they have to update these policies.”

One visitor at the Reina Sofía Wednesday, Richard Rottman of Los Angeles, called “Guernica” an important Picasso shortly after someone tapped his shoulder.

“I was in the way of their photo,” he said, laughing.

This article originally appeared in The New York Times.