Description

With the schileren technique of photography, changes in density of air or other gases are made colorfully visible. Heat and pressure both change the density of air; thus, this photograph of the vortices produced by a metal fan blade rotating at 3600 rpm through the flame of an alcohol burner is particularly revealing. The light from the flash passes through an aperture, where it is filtered, and then enters the large concave mirrors. The camera, or eye, is aligned with the light coming off the array of mirrors and through another limiting aperture. The phenomenon, occurring within the array, is illuminated from behind, thus silhouetting the objects and making visible the refraction of light caused by the varying densities of the atmosphere. Edgerton collaborated for many years with his assistant Kim Vandiver in developing this special photographic technique. (see "Stopping Time" (1987) pp. 136-7). (CC)