File:Tesla colorado adjusted.jpg

English: Publicity photo of Serbian-American inventor Nikola Tesla in December 1899 sitting in his laboratory in Colorado Springs next to his magnifying transmitter high voltage generator while the machine produced huge bolts of electricity.

This image was created by Century Magazine photographer Dickenson V. Alley using "trick photography" via a double exposure. The electrical bolts were photographed in a darkened room. The photographic plate was exposed a second time with the equipment off and Tesla sitting in the chair. In his Colorado Springs Notes Tesla admitted the photo was a double exposure:

To give an idea of the magnitude of the discharge the experimenter is sitting slightly behind the "extra coil". I did not like this idea but some people find such photographs interesting. Of course, the discharge was not playing when the experimenter was photographed, as might be imagined!

and this is confirmed by Tesla biographers Carl Willis and Marc Seifer.

In 1899-1900 Tesla built the laboratory and researched wireless electric power transmission there. The "magnifying transmitter", one of the largest Tesla coils ever built, with an input power of 300 kW generated voltages on the order of 12 million volts at frequencies around 150 kHz, producing 140 ft. (41 m) "lightning" bolts.