American Scientist

January-February 2006

Volume: 94 Number: 1

A .22-caliber bullet easily penetrates a telephone directory perched on a stool, but the gunshot's effect on the surrounding environment is the photographer's actual target. Turbulence and shock waves can be revealed by specialized high-speed photography technology combined with classical imaging techniques, as Gary S. Settles describes in "High-speed Imaging of Shock Waves, Explosions and Gunshots." Here the color schlieren method uses distortions of a background pattern to capture invisible phenomena. Large-scale, high-speed images of shock waves are of use in ballistics, forensics and hardening aircraft and buildings against explosions. Other techniques, such as the direct-illumination image of a .22-caliber bullet striking a ball-point pen, can reveal shrapnel patterns from gunshots and explosions. (Photographs courtesy of Gary S. Settles.)