Science / Medicine : Photography by Hindsight

A “photographic time machine” that permits researchers to photograph events that occur before the camera’s shutter is opened has been developed by scientists at the National Institute of Standards and Technology in Gaithersburg, Md.

The new system is an arrangement of optical components, including mirrors and a crystal shutter, that stores optical images of an event long enough for the shutter of a high-speed camera to be opened, said physicist Edward F. Kelley, its inventor.

Researchers now take pictures of lightning, for example, by pointing a camera toward a storm and leaving the shutter open until a bolt strikes. Images of events immediately preceding the strike are thus overwhelmed by light from the strike itself, Kelley said.

But with the new system, the flash of lightning triggers the shutter, which is then opened just long enough to catch the delayed image of the first phases of the flash. “Functionally, the optical delay is equivalent to forcing the image to travel an additional 120 meters before it gets to the camera,” Kelley said.