Both film and digital photography rely on light exposure. With traditional analog photography, it’s the film itself that is being exposed by light. Digital cameras have a CMOS sensor that is exposed by light in a similar way. For any given type of film or CMOS sensor, a certain amount of light is required to get a properly-exposed photo. When all other settings remain fixed, the only way to get a good photo is to have a lot of light or a long exposure time. But long exposure times result in motion blur, which is why Tyler Gerritsen built a DIY high-speed LED flash called Edgerton.
Flash photography is, of course, nothing new. There is a reason photography studios use incredibly bright lights — it’s the only way to get a good photo without increasing the exposure time. High-speed flashes are often used in situations where motion blur is a concern, such as when capturing sporting events. But when things are moving really fast, commercial flash units often fall short. Gerritsen likes to take ballistic photographs of bullets striking glass, and built a ballistic chronograph to get the timing down right. But standard speedlight flashes still couldn’t keep up, and introduced motion blur.
His solution was to build his own LED flash that could respond extremely quickly with a sufficient brightness. To do that, he used 12 Cree XLamp LEDs along with the capacitors, MOSFETs, and a boost regulator to drive them. Those are controlled by an ATmega328P microcontroller. All of those components are housed in a 3D-printed enclosure. The capacitors are energized before the shot, and are then set to discharge at the proper time. The flash goes off for just one microsecond, which is perfect for this kind of photography. By timing the flash and camera’s shutter release just right with the trigger pull, Gerritsen is able to take beautiful photos of extremely fast-moving bullets.