In the photo below, you can see shotgun buckshot being blasted through the air at around a thousand feet per second (350m/s). And those thin waves that appear in the image surrounding the pellets? That's actually the wave of compressed air being pushed along by the projectiles. A company called MetroLaser was able to take this high-speed photo using a new digital photography system they developed to work with optical streak photography. In theory, their camera system can capture photos of objects moving at up to 7,500 miles per hour. That's ten times the speed of sound.
Streak photography is a proven technique for taking photos of fast-moving objects. In its conventional implementation, an object flies past a camera lens, and the light bouncing off of it goes through a system composed of a thin slit, field and relay lenses, and a high-spinning mirror to split the image up into precise increments saved on film that can be composited later. The new system developed by MetroLaser replaces the film at the end of that chain (which is no longer produced) with a modern digital camera, which can produce full-color photos after post-processing of the image streak.
What makes the system work is the precise timing of the spinning mirror. As MetroLaser's Benjamin Buckner explained to Phys.org, "the galvo mirror tracks the object as it moves past the camera and directs the right portion of the object's image onto the right portion of the image sensor in order to form a complete, undistorted image. This has to be done in a few thousandths of a second." It's complicated, but the approach of using this kind of lens and mirror rig lets researchers potentially turn any consumer DSLR into a high-speed streak camera. One proposed application--using the camera system to determine the finishing order of high-speed races.