Museumgoers snapping photos of Vincent van Gogh’s Starry Night, 1889, at MoMA. ©2013 REBECCA ROBERTSON

It’s a scene that plays itself out hundreds of times a day in American museums: a mother and her fidgety teenage daughter stand before a famous painting—in this case, Caravaggio’s The Toothpuller, from the early 17th century. The mom pulls out a cell phone and poses her daughter in front of the work, a funny-grotesque image of a smirking dentist performing an extraction. As she frames the shot, a guard steps forward. “No photos,” he says. The woman apologizes. She and her daughter slip out of the room and continue on to the next gallery.

This particular episode took place at the Los Angeles County Museum of Art (LACMA), at a traveling exhibition devoted to Caravaggio’s influence on European painting. But it could have happened anywhere. We’re in an age when people take pictures just about everywhere, an act that photography critic Jörg M. Colberg describes as “compulsive looking.” The phenomenon has created a unique set of challenges for art museums, many of which have historically had strict limitations on photography—either for the purpose of protecting light-sensitive works or because of copyright issues.

But the ubiquity of digital cameras, along with the irrepressible urge to take pictures, has led many museums to revise their policies in recent years. Institutions such as the Metropolitan Museum of Art, the Art Institute of Chicago, the National Gallery of Art, the Indianapolis Museum of Art, and the Getty Museum—to name a few—all allow photography in some or all of their permanent-collection spaces.

“You are fighting an uphill battle if you restrict,” says Nina Simon, director of the Santa Cruz Museum of Art & History and author of The Participatory Museum. “Even in the most locked-down spaces, people will still take pictures and you’ll still find a million of these images online. So why not support it in an open way that’s constructive and embraces the public?”

Certainly, there are practical reasons for doing so. No-photo policies can be difficult to enforce. “Guards are spending so much time focusing on someone holding a device that they might not see the person next to them touching the art,” says Alisa Martin, senior manager of brand management and visitor services at the Brooklyn Museum, an institution that has allowed photography in the majority of its galleries for roughly half a dozen years. “As the devices get smaller, it gets harder to manage. We have to ask ourselves, are we using our guards appropriately?”

Social media also complicates the issue. This past January, the Pew Research Center’s Internet & American Life Project reported that 97 percent of the more than 1,200 arts organizations it polled had a presence on platforms like Twitter, YouTube, and Flickr. New York’s Museum of Modern Art, for example, posts photos of artworks and installation processes on Facebook (where it has around 1.3 million followers), the Massachusetts Museum of Contemporary Art has photos of its Sol LeWitt wall drawings on Instagram, and various other institutions—from the San Francisco Museum of Modern Art to the Albright-Knox Art Gallery in Buffalo—can be found on the picture-sharing and blogging service Tumblr. Moreover, places like the Brooklyn Museum and LACMA have high-resolution images from their collections available for free on their websites.

With museums sharing so much imagery themselves, it can be difficult for visitors to understand that they can’t necessarily do the same. “If a museum is really active on social media, they’re putting forward the idea that they represent a venue that is all about being conversational,” says Simon. “For the visitor, it can be disturbing to then go to the physical space and be confronted with a policy that isn’t.” (For the record, both MoMA and MASS MoCA allow photography in most of their spaces. And while there’s no way to quantify which artwork gets the most photographic attention, a staff member at MoMA suspects it’s Vincent van Gogh’s 1889 painting Starry Night for that museum.)

The biggest hurdle to wide-open photo policies is the issue of copyright. Museums often do not hold the copyrights to the works they display, which creates legal problems when visitors start snapping away. According to Julie Ahrens, a lawyer who specializes in issues of copyright and fair use at the Center for Internet and Society at Stanford University, a photograph of an artwork could be considered a “derivative work,” which is “potentially a violation of the copyright holder.” But the deluge of cameras, along with the fact that the vast majority of visitors simply want to snap a pic for a Facebook album, has led some institutions—such as MoMA, the Indianapolis Museum, and the Brooklyn Museum—to ask lenders for permission to shoot, with the stipulation that pictures are for noncommercial use.

“There’s an undeniable benefit to having visitors tweet about their visit or share photos,” says Brooke Fruchtman, associate vice president of public engagement at LACMA. “We’ve had great success with our Stanley Kubrick exhibition because people could take pictures of anything.” For more than a year, the museum has allowed photography in its permanent-collection galleries. Still, for temporary shows, permission ultimately rests in the hands of the lender, as in the case of Caravaggio’s Toothpuller, which is owned by the Galleria Palatina at the Pallazzo Pitti in Florence.

Naturally, there are museumgoers who will occasionally break the rules: a visitor to the Indianapolis Museum recently took pictures all over the building—including galleries that were off limits to photography—and then offered them for sale online. “We had to intervene,” says Anne Young, who oversees rights and reproduction for the museum. This type of behavior, however, is an extreme exception.

For years, advocates of open-source culture and a growing chorus of art bloggers have lobbied for less restrictive photo policies on the grounds that our shared artistic legacy is intended to be, well, shared. Not to mention that there is no small irony in being forbidden to take pictures in cultural establishments that celebrate the work of artists like Andy Warhol, Sherrie Levine, and Richard Prince, figures whose work is based, to a large degree, on the photographs of others.

As a culture, we increasingly communicate in images. Twenty years ago, a museumgoer might have discussed an interesting work of art with friends over dinner. Today, that person is more likely to take a picture of it and upload it to Facebook—such as New York magazine critic Jerry Saltz, who, earlier this year, posted a photo of himself hamming it up in front of a Marcel Duchamp at the Philadelphia Museum of Art. Or perhaps that museumgoer might remix his or her photo with other visual elements and transform it into something new. Every day, users on image-sharing sites such as Tumblr create their own diptychs, collages, and themed galleries devoted to everything from ugly Renaissance babies to Brutalist architecture.

This transformation in the way in which people digest visual stimuli—not to mention the rest of the world around them—is something that Harvard theoretician Lawrence Lessig has described as a shift from “read-only” culture (in which a passive viewer looks upon a work of art) to “read-write” culture (in which the viewer actively participates in a recreation of it). The first step toward recreating a work of art, for most people, is to photograph it, which, ultimately, isn’t all that different from the time-honored tradition of sketching.

Carolina A. Miranda is an independent journalist based in Los Angeles. She blogs at C-Monster.net.