LAST year, Anne Hawley, the longtime director of the Isabella Stewart Gardner Museum, in Boston, was admiring an 18th-century French painting at the Louvre.

Suddenly, she said, a group of tourists with cameras elbowed her out of the way so they could photograph the painting. Then they moved on to the next one, and the next one, each time emitting a fusillade of flashes.

“It was appalling,” Ms. Hawley said. “I had to leave the gallery.”

Ms. Hawley hopes that never happens at the Gardner, which reopened in January after adding a new wing. So the museum’s photo policy, at least in the original building, remains the same as before: no photography permitted.

That makes the Gardner a rare holdout in the museum world. These days, visitors tend to carry phones with cameras — and, in many cases, want to share images on social media.