Excuse me. Just a moment, please. Consider the source! This photograph was produced and published by the Brady studio. Brady was careful to include himself in many of his famous war images -- it helped solidify his reputation as the war photographer. He created the title for the image. It could just have easily been titled "Look at Me! I'm the Dauntless Photographer Staring Into the Eyes of the Enemy!" Okay, fair enough, you might think, if he did make this image under fire why not say so? For decades this image was taken on faith as just what it was called.
However, photographic historians have debunked the photo and they did so without breaking a sweat. The technological constraints of photography in this period were such that figures were required to stay motionless for several seconds -- as much as thirty seconds depending on light conditions. Although you probably can't make it out on your screen, the U.S. flag in the background is blurred, showing that it was flapping in the wind during the exposure of the picture. And yet all the men are clear and unblurred, meaning that they held still for the picture.
Now think about it: can you imagine a crowd of some two dozen men standing perfectly still for the period of time required to compose the image and make the exposure -- during an artillery bombardment? Oh, Mr. Brady, you humbug! This picture is a publicity stunt worthy of your friend, P.T. Barnum.
Reading between the lines becomes easier with practice, and it also becomes easier with more specialized knowledge. Without knowing how photographs were made in the Civil War you might not be able to deconstruct this picture. But if you have the facts and you consider the source -- aha! You discover you have a document that is interesting in a very different way than what you thought you had at first. Facts and logic are two indispensable tools for writing nonfiction. Consider the source!