Allegedly, this special method of photographing objects allows the taking of pictures of paranormal forces or auras. Actually, what is recorded is due to quite natural phenomena such as pressure, electrical grounding, humidity and temperature.
In 1939, Semyon Kirlian, a Russian, discovered by accident that if an object on a photographic plate is subjected to a high-energy electric field, an image is created on the plate. The image looks like colored halo or corona discharge. This image is said to be a physical manifestation of the spiritual aura which allegedly surrounds each living thing.
This method of photography has its practical uses, however, as changes in, or amounts of, electromagnetic radiation may be an indicator of a medical problem. But, there is nothing supernatural or paranormal about coronas. Nor is it true, as is sometimes claimed by occultists, that if an object such as a leaf is torn and photographed the aura of the whole leaf, a "phantom" leaf, appears. If an outline of a whole leaf appears where only a half leaf should be it is because there is a residue from the whole leaf remaining on the photographic plate or film.
further reading
"A Study of the Kirlean Effect," Arleen J. Watkins and William S. Bickel in The Hundreth Monkey and Other Paradigms of the Paranormal,ed. Kendrick Frazier (Buffalo, N.Y.: Prometheus Books, 1991), pp. 209-221.