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 of the gradation by Herscheleffekt. The top image is copied from a hard negative and on a hard paper (copy time 20 sec.). The lower image has been copied for 50 sec. and then afterlit for 30 min. During a red filter in daylight. For more info see: Bäckström, Helmer. Photographic manual. Nature and Culture. Stockholm. 1942. p. 302.

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Size: 1935px × 2583px
Photo credit: © BTEU/TEKNISKA / Alamy / Afripics
License: Licensed
Model Released: No

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