Skiopticon image from the Department of Photography at the Royal Institute of Technology. Use by Professor Helmer Bäckström as lecture material. Bäckström was Sweden's first professor in photography at the Royal Institute of Technology in Stockholm 1948-1958. Curves for longevity, light flow, effect and light exchange in a light bulb as functions of rated voltage and operating voltage. For more info see: Bäckström, Helmer. Photographic manual. Nature and Culture. Stockholm. 1942. p. 780.

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Size: 1936px × 2581px
Photo credit: © BTEU/TEKNISKA / Alamy / Afripics
License: Licensed
Model Released: No

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