They have raised questions about whether photos have the same power now to sway public opinion and political will; about the increasingly sophisticated ways an image-saturated public reads a picture’s racial and political subtext; and about the rapid transformation of the protests, even more so than the Los Angeles riots or the Occupy movement, into a war of images. The war pits what appears to be a large-scale paramilitary police presence against crowds of African-American protesters walking with their hands raised in surrender — or people throwing things and looting.

The Philadelphia Daily News was a case in point in the speed with which 21st-century image parsing can occur. In the wee hours of Thursday morning — in response to readers’ comments on Twitter about a photo the newspaper had planned to run on its front page, showing an African-American protester in Ferguson about to hurl what looked like a firebomb — editors changed their minds and instead used a photograph of an African-American woman standing in front of police officers, holding a sign urging answers in the death of the teenager, Michael Brown.

An assistant city editor wrote on Twitter to those objecting to the first picture that they would be able to understand the whole story, in a “sympathetic treatment,” if they opened the paper. But a reader responded, “Yes, in ten-point font I can see the fine print, which is completely overwhelmed by the picture.”

In the civil rights era, the visual stamp of the movement was determined by newspapers and the nightly news. Today, the imagery one sees depends on the filters one uses. One person’s Twitter feed may be full of footage of police firing tear gas or of peaceful protesters with their hands up. But David J. Garrow, a historian at the University of Pittsburgh’s law school and the author of several books on the civil rights movement, noted that when he searched for images of Ferguson on Google, roughly half showed what appeared to be looting.