Post count whoring.
"Figure 10. Color schlieren and black-and-white shadowgraph techniques capture similar information but emphasize complementary details. A microsecond color schlieren photograph (left) captures an instant during the firing of a .22-caliber marksman's pistol. The air shock wave and the transonic bullet have left the muzzle, followed by the propellant gases. The muzzle blast is the "bang" that one hears upon firing a gun. Toward the right side of the image, thermal convection rises from the gun and the shooter’s hand. A frame from a high-speed shadowgraph video (right) shows the firing of a single round from an AK-47 submachine gun, with its spherical muzzle blast and supersonic bullet trailing oblique shock waves.
Photographs courtesy of Gary S. Settles. "