When Cullen finds a photograph of Johnson's unit, giving him the name of the sergeant he is looking for, the faces of some of the men are blurry, including the sergeant. This is not some type of editing mistake, photography during the Civil War was still fairly primitive, depending on the ambient lighting the camera film would need anywhere from five to 20 seconds of exposure (whereas a modern camera only needs a fraction of a second). This required the subjects of the photo to hold absolutely still, any movement of the head would cause the subject's face to be blurred in the photo.