NEW YORK (AP) -- Television is a visual medium, and when news producers get video illustrating a major story like the Boston marathon explosions, their job is to put it on the air.
At some point it becomes a reel of constant chaos. Images showing the flash of explosions, stunned people running for safety, injured victims rushed to ambulances are repeated onscreen to the extent that it can become as disturbing as the event itself. Boston wasn't the first time this has happened and won't be the last, not with half the populace walking around with video cameras in their pocket.
Even more than 24 hours later on Tuesday, cable news networks were repeating some of the same video regularly in following up the story.
"It's hard to turn away," said Emily Godbey, an Iowa State University professor with an expertise in images of disasters. "But it might be healthy, when you've absorbed the current event, to turn away."
In the hours directly following the explosions, cable and broadcast news aired video almost as quickly as it came in and with little breaks. Anchors like Brian Williams, Diane Sawyer, Scott Pelley narrated the action but you rarely — if ever — saw their faces.
"If you're in a news department and an event like this happens, it's your job to put it on the air. Period," said Rick Kaplan, a longtime TV news producer and executive.
Kaplan watched the coverage closely and pronounced it solid and compelling. But he reached the point, without a dramatic break in the story such as an indication of who was responsible, that he had to call it quits. It was too much. The same footage shown Tuesday was nothing more than "wallpaper," an industry term referring to video shown because it's exciting even as it has lost much news purpose.
As the story is breaking, broadcasters must also be conscious of new viewers tuning who are new to the story, to fill them in on what is happening. That generally takes precedence over concerns about people who have spent a long time watching the same news over and over.
"Video is important information, particularly in the early stages of a story," said former ABC News President David Westin. "Sometimes it's the only information you have."
That value diminishes the further you get into a story, unless new video emerges that presents different evidence, he said. The challenge for news executives is identifying the time at which the video has ceased becoming informative and simply serves to desensitize the viewer.
Westin was ABC News president during the Sept. 11 attacks. He called a halt to showing replays of the planes striking the World Trade Center in the days after the event after being told that they were becoming disturbing to some children who couldn't grasp that they were not different events.
"The television coverage itself can become an instrument of terror if you're not careful," he said.
While these issues need to be considered by news executives, "the first thing for a journalist is to cover the story," he said. "If a journalist spends an amount of time not doing stories to protect the audience, it's not a good thing."
It's not just television audiences that can be disturbed by repeated exposure to video of these events. Westin said ABC offered counseling to its producers after events like Columbine to stave off the effects of constantly being exposed to these images as part of their work.
In some respects, coverage of the Boston explosions was more visually gruesome than the Sept. 11 attacks, Godbey said. Even though thousands of people were killed on Sept. 11, there were very few people injured. The Boston aftermath had dozens of people hurt.
The still images of Boston have proved gorier than what was on television. The New York Daily News and Post ran the same front page picture on Tuesday of a woman sitting on a sidewalk streaked with blood.
Even if the images are overwhelming and repetitive, or if some of the details prove later to be wrong, that's far better than an alternative of little information in the wake of a tragedy, said Paul Levinson, a communications professor at Fordham University. The price of people who may be disturbed by repeated images is worth the advantages of today's information age, where many people have smartphones and are able to deliver news quickly.
Imagine, he said, what it would have been like in 1963 if smartphones existed when President Kennedy was shot in Dallas.
"What happened in Boston is a tragically ideal example of how we get our information these days," he said.