After the Sandy Hook massacre, Michael Moore wrote that he hoped photographs of the dead children would be leaked, perhaps by a grieving parent. If so, “the jig will be up” for the National Rifle Association, he confidently predicted. “The debate on gun control will come to an end. There will be nothing left to argue over.”

This is childish thinking. Photographs tend to start arguments, not end them. And Mr. Moore could not have been more mistaken about the desires of the Sandy Hook parents. Partly in response, some of them pushed, successfully, for the passage of SB 1149, a Connecticut law that prohibits the disclosure of photographs and digital images of homicide victims. This raises another unresolved but increasingly exigent question: Do such photographs belong to the police, the F.B.I., the parents or the public? How to balance a family’s right to privacy with the public’s right to know?

There are many examples of photographs that gave history a nudge — sometimes even a vigorous one. Think of the My Lai massacre photographs, of the Abu Ghraib torture photos taken by American troops and of Darnella Frazier’s phone video of George Floyd’s murder. But just as the Till photograph didn’t end Jim Crow, the My Lai images didn’t end the Vietnam War (nor did press reports of the atrocity), the Abu Ghraib photographs didn’t end the Iraq war (or even lead to high-level prosecutions), and the Floyd video didn’t end police brutality. These photographs did support, encourage and strengthen public perceptions, political movements and public debates that were already in play. But none resulted in the kinds of immediate change that their supporters hoped for. When it comes to images, there are few Damascene moments, which is why most photojournalists are modest, if not pessimistic, about the influence of their work.