RAPATRONIC RAP

         With the Fourth of July a few days away, it’s appropriate to have a look at what had to have been the biggest firecracker of its time.  As part of the Tumbler-Snapper series of nuclear tests, this bomb was detonated above the Nevada desert in 1952.  The image was captured one millisecond after the explosion, with the fireball reaching a mere sixty-six feet across.  The spikes at its base are known as the rope trick effect, bright streaks caused by the vaporization of the cables supporting the test tower.

            Legendary scientist-researcher-professor-engineer and photographer Harold “Papa Flash” Edgerton used a rapatronic camera – a revolutionary high-speed device of his own design – to freeze a moment that was invisible to the human eye.  It used two polarizing filters set at ninety degrees, which normally blocked light.  At detonation, an electrical pulse activated a cell placed between them, rotating the light’s polarization just long enough for a brief exposure to pass through the aperture.  In his earlier stroboscopic photography with Charles Wyckoff, Edgerton used short, intense flashes of light to freeze fast action on film.  For the rapatronic camera, that logic was inverted: Instead of lighting a subject with repeated flashes, the camera used the explosion’s own light to trigger an exposure that lasted a fraction of a second.  Its shutter had no moving parts and controlled exposure by switching a magnetic field on and off at extremely high speed.  By any measure, it was a considerable achievement; its principles are still in use today.

            In addition to his highly honored career as a scientist, Edgerton’s photographic legacy is equally impressive.  He turned photography into a tool for seeing the unseen – ultra-fast motion, strobe-frozen action and events too brief for the naked eye.  His work made the electronic flash practical and produced iconic images you’re no doubt familiar with: The milk-drop crown, the bullet-through-an-apple and the hummingbird in flight.

            Edgerton was an inventor and an artist, which is why his influence crosses science, engineering, military imaging, underwater exploration and fine art photography.  He refined stroboscopic methods into repeatable imaging systems and held dozens of patents related to strobe and electrical devices.  His photographs were exhibited early and entered major museum collections, helping establish high-speed scientific imagery as a serious art.

            His legacy can be witnessed in modern flash photography, motion-analysis imaging, and experimental visual research that depends on freezing time at high precision.  During World War II and after, his lighting and imaging work also supported aerial reconnaissance, sonar and underwater exploration (with Jacques Cousteau).  MIT’s Edgerton Center and digital collections continue to preserve and extend his methods and archival material.

            Edgerton was a great talent and a great American. Study up on him when you get the chance.  His work is incredible!

An early model of the rapatronic camera.